diff --git a/config/formats.ts b/config/formats.ts
index 76a4178770895..ed5dadaf89ddd 100644
--- a/config/formats.ts
+++ b/config/formats.ts
@@ -2901,7 +2901,7 @@ export const Formats: import('../sim/dex-formats').FormatList = [
 		onValidateSet(set, format, setHas, teamHas) {
 			if (set.item) {
 				const item = this.dex.items.get(set.item);
-				if (item.megaEvolves && !(this.ruleTable.has(`+item:${item.id}`) || this.ruleTable.has(`+pokemontag:mega`))) {
+				if (item.megaStone && !(this.ruleTable.has(`+item:${item.id}`) || this.ruleTable.has(`+pokemontag:mega`))) {
 					return [`Mega Evolution is banned.`];
 				}
 				if (item.zMove && !(this.ruleTable.has(`+item:${item.id}`))) {
@@ -3680,8 +3680,8 @@ export const Formats: import('../sim/dex-formats').FormatList = [
 			}
 			const item = this.dex.items.get(set.item);
 			if (set.item && item.megaStone) {
-				const megaSpecies = this.dex.species.get(Array.isArray(item.megaStone) ? item.megaStone[0] : item.megaStone);
-				if (item.megaEvolves?.includes(species.baseSpecies) && megaSpecies.bst > 625) {
+				const megaSpecies = this.dex.species.get(item.megaStone[species.baseSpecies]);
+				if (megaSpecies.bst > 625) {
 					return [
 						`${set.name || set.species}'s item ${item.name} is banned.`, `(Pok\u00e9mon with a BST higher than 625 are banned)`,
 					];
diff --git a/data/items.ts b/data/items.ts
index 1ffb717568813..fa452c1c48032 100644
--- a/data/items.ts
+++ b/data/items.ts
@@ -22,12 +22,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	abomasite: {
 		name: "Abomasite",
 		spritenum: 575,
-		megaStone: "Abomasnow-Mega",
-		megaEvolves: "Abomasnow",
+		megaStone: { "Abomasnow": "Abomasnow-Mega" },
 		itemUser: ["Abomasnow"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 674,
 		gen: 6,
@@ -36,12 +34,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	absolite: {
 		name: "Absolite",
 		spritenum: 576,
-		megaStone: "Absol-Mega",
-		megaEvolves: "Absol",
+		megaStone: { "Absol": "Absol-Mega" },
 		itemUser: ["Absol"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 677,
 		gen: 6,
@@ -50,12 +46,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	absolitez: {
 		name: "Absolite Z",
 		spritenum: 576,
-		megaStone: "Absol-Mega-Z",
-		megaEvolves: "Absol",
+		megaStone: { "Absol": "Absol-Mega-Z" },
 		itemUser: ["Absol"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2588,
 		gen: 9,
@@ -141,12 +135,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	aerodactylite: {
 		name: "Aerodactylite",
 		spritenum: 577,
-		megaStone: "Aerodactyl-Mega",
-		megaEvolves: "Aerodactyl",
+		megaStone: { "Aerodactyl": "Aerodactyl-Mega" },
 		itemUser: ["Aerodactyl"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 672,
 		gen: 6,
@@ -155,12 +147,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	aggronite: {
 		name: "Aggronite",
 		spritenum: 578,
-		megaStone: "Aggron-Mega",
-		megaEvolves: "Aggron",
+		megaStone: { "Aggron": "Aggron-Mega" },
 		itemUser: ["Aggron"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 667,
 		gen: 6,
@@ -225,12 +215,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	alakazite: {
 		name: "Alakazite",
 		spritenum: 579,
-		megaStone: "Alakazam-Mega",
-		megaEvolves: "Alakazam",
+		megaStone: { "Alakazam": "Alakazam-Mega" },
 		itemUser: ["Alakazam"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 679,
 		gen: 6,
@@ -250,12 +238,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	altarianite: {
 		name: "Altarianite",
 		spritenum: 615,
-		megaStone: "Altaria-Mega",
-		megaEvolves: "Altaria",
+		megaStone: { "Altaria": "Altaria-Mega" },
 		itemUser: ["Altaria"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 755,
 		gen: 6,
@@ -264,12 +250,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	ampharosite: {
 		name: "Ampharosite",
 		spritenum: 580,
-		megaStone: "Ampharos-Mega",
-		megaEvolves: "Ampharos",
+		megaStone: { "Ampharos": "Ampharos-Mega" },
 		itemUser: ["Ampharos"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 658,
 		gen: 6,
@@ -350,12 +334,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	audinite: {
 		name: "Audinite",
 		spritenum: 617,
-		megaStone: "Audino-Mega",
-		megaEvolves: "Audino",
+		megaStone: { "Audino": "Audino-Mega" },
 		itemUser: ["Audino"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 757,
 		gen: 6,
@@ -397,12 +379,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	banettite: {
 		name: "Banettite",
 		spritenum: 582,
-		megaStone: "Banette-Mega",
-		megaEvolves: "Banette",
+		megaStone: { "Banette": "Banette-Mega" },
 		itemUser: ["Banette"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 668,
 		gen: 6,
@@ -411,12 +391,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	barbaracite: {
 		name: "Barbaracite",
 		spritenum: 564,
-		megaStone: "Barbaracle-Mega",
-		megaEvolves: "Barbaracle",
+		megaStone: { "Barbaracle": "Barbaracle-Mega" },
 		itemUser: ["Barbaracle"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2581,
 		gen: 9,
@@ -425,12 +403,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	baxcalibrite: {
 		name: "Baxcalibrite",
 		spritenum: 0,
-		megaStone: "Baxcalibur-Mega",
-		megaEvolves: "Baxcalibur",
+		megaStone: { "Baxcalibur": "Baxcalibur-Mega" },
 		itemUser: ["Baxcalibur"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2601,
 		gen: 9,
@@ -446,12 +422,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	beedrillite: {
 		name: "Beedrillite",
 		spritenum: 628,
-		megaStone: "Beedrill-Mega",
-		megaEvolves: "Beedrill",
+		megaStone: { "Beedrill": "Beedrill-Mega" },
 		itemUser: ["Beedrill"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 770,
 		gen: 6,
@@ -582,12 +556,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	blastoisinite: {
 		name: "Blastoisinite",
 		spritenum: 583,
-		megaStone: "Blastoise-Mega",
-		megaEvolves: "Blastoise",
+		megaStone: { "Blastoise": "Blastoise-Mega" },
 		itemUser: ["Blastoise"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 661,
 		gen: 6,
@@ -596,12 +568,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	blazikenite: {
 		name: "Blazikenite",
 		spritenum: 584,
-		megaStone: "Blaziken-Mega",
-		megaEvolves: "Blaziken",
+		megaStone: { "Blaziken": "Blaziken-Mega" },
 		itemUser: ["Blaziken"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 664,
 		gen: 6,
@@ -762,12 +732,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	cameruptite: {
 		name: "Cameruptite",
 		spritenum: 625,
-		megaStone: "Camerupt-Mega",
-		megaEvolves: "Camerupt",
+		megaStone: { "Camerupt": "Camerupt-Mega" },
 		itemUser: ["Camerupt"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 767,
 		gen: 6,
@@ -793,12 +761,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	chandelurite: {
 		name: "Chandelurite",
 		spritenum: 557,
-		megaStone: "Chandelure-Mega",
-		megaEvolves: "Chandelure",
+		megaStone: { "Chandelure": "Chandelure-Mega" },
 		itemUser: ["Chandelure"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2574,
 		gen: 9,
@@ -822,12 +788,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	charizarditex: {
 		name: "Charizardite X",
 		spritenum: 585,
-		megaStone: "Charizard-Mega-X",
-		megaEvolves: "Charizard",
+		megaStone: { "Charizard": "Charizard-Mega-X" },
 		itemUser: ["Charizard"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 660,
 		gen: 6,
@@ -836,12 +800,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	charizarditey: {
 		name: "Charizardite Y",
 		spritenum: 586,
-		megaStone: "Charizard-Mega-Y",
-		megaEvolves: "Charizard",
+		megaStone: { "Charizard": "Charizard-Mega-Y" },
 		itemUser: ["Charizard"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 678,
 		gen: 6,
@@ -903,12 +865,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	chesnaughtite: {
 		name: "Chesnaughtite",
 		spritenum: 558,
-		megaStone: "Chesnaught-Mega",
-		megaEvolves: "Chesnaught",
+		megaStone: { "Chesnaught": "Chesnaught-Mega" },
 		itemUser: ["Chesnaught"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2575,
 		gen: 9,
@@ -978,12 +938,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	chimechite: {
 		name: "Chimechite",
 		spritenum: 0,
-		megaStone: "Chimecho-Mega",
-		megaEvolves: "Chimecho",
+		megaStone: { "Chimecho": "Chimecho-Mega" },
 		itemUser: ["Chimecho"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2587,
 		gen: 9,
@@ -1130,12 +1088,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	clefablite: {
 		name: "Clefablite",
 		spritenum: 544,
-		megaStone: "Clefable-Mega",
-		megaEvolves: "Clefable",
+		megaStone: { "Clefable": "Clefable-Mega" },
 		itemUser: ["Clefable"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2559,
 		gen: 9,
@@ -1258,12 +1214,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	crabominite: {
 		name: "Crabominite",
 		spritenum: 0,
-		megaStone: "Crabominable-Mega",
-		megaEvolves: "Crabominable",
+		megaStone: { "Crabominable": "Crabominable-Mega" },
 		itemUser: ["Crabominable"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2595,
 		gen: 9,
@@ -1357,12 +1311,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	darkranite: {
 		name: "Darkranite",
 		spritenum: 0,
-		megaStone: "Darkrai-Mega",
-		megaEvolves: "Darkrai",
+		megaStone: { "Darkrai": "Darkrai-Mega" },
 		itemUser: ["Darkrai"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2593,
 		gen: 9,
@@ -1425,12 +1377,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	delphoxite: {
 		name: "Delphoxite",
 		spritenum: 559,
-		megaStone: "Delphox-Mega",
-		megaEvolves: "Delphox",
+		megaStone: { "Delphox": "Delphox-Mega" },
 		itemUser: ["Delphox"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2576,
 		gen: 9,
@@ -1454,12 +1404,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	diancite: {
 		name: "Diancite",
 		spritenum: 624,
-		megaStone: "Diancie-Mega",
-		megaEvolves: "Diancie",
+		megaStone: { "Diancie": "Diancie-Mega" },
 		itemUser: ["Diancie"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 764,
 		gen: 6,
@@ -1521,12 +1469,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	dragalgite: {
 		name: "Dragalgite",
 		spritenum: 565,
-		megaStone: "Dragalge-Mega",
-		megaEvolves: "Dragalge",
+		megaStone: { "Dragalge": "Dragalge-Mega" },
 		itemUser: ["Dragalge"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2582,
 		gen: 9,
@@ -1564,12 +1510,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	dragoninite: {
 		name: "Dragoninite",
 		spritenum: 547,
-		megaStone: "Dragonite-Mega",
-		megaEvolves: "Dragonite",
+		megaStone: { "Dragonite": "Dragonite-Mega" },
 		itemUser: ["Dragonite"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2562,
 		gen: 9,
@@ -1615,12 +1559,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	drampanite: {
 		name: "Drampanite",
 		spritenum: 569,
-		megaStone: "Drampa-Mega",
-		megaEvolves: "Drampa",
+		megaStone: { "Drampa": "Drampa-Mega" },
 		itemUser: ["Drampa"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2585,
 		gen: 9,
@@ -1714,12 +1656,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	eelektrossite: {
 		name: "Eelektrossite",
 		spritenum: 556,
-		megaStone: "Eelektross-Mega",
-		megaEvolves: "Eelektross",
+		megaStone: { "Eelektross": "Eelektross-Mega" },
 		itemUser: ["Eelektross"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2573,
 		gen: 9,
@@ -1889,12 +1829,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	emboarite: {
 		name: "Emboarite",
 		spritenum: 552,
-		megaStone: "Emboar-Mega",
-		megaEvolves: "Emboar",
+		megaStone: { "Emboar": "Emboar-Mega" },
 		itemUser: ["Emboar"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2569,
 		gen: 9,
@@ -1946,12 +1884,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	excadrite: {
 		name: "Excadrite",
 		spritenum: 553,
-		megaStone: "Excadrill-Mega",
-		megaEvolves: "Excadrill",
+		megaStone: { "Excadrill": "Excadrill-Mega" },
 		itemUser: ["Excadrill"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2570,
 		gen: 9,
@@ -2031,12 +1967,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	falinksite: {
 		name: "Falinksite",
 		spritenum: 570,
-		megaStone: "Falinks-Mega",
-		megaEvolves: "Falinks",
+		megaStone: { "Falinks": "Falinks-Mega" },
 		itemUser: ["Falinks"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2586,
 		gen: 9,
@@ -2052,12 +1986,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	feraligite: {
 		name: "Feraligite",
 		spritenum: 549,
-		megaStone: "Feraligatr-Mega",
-		megaEvolves: "Feraligatr",
+		megaStone: { "Feraligatr": "Feraligatr-Mega" },
 		itemUser: ["Feraligatr"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2564,
 		gen: 9,
@@ -2252,12 +2184,11 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	floettite: {
 		name: "Floettite",
 		spritenum: 562,
-		megaStone: "Floette-Mega",
-		megaEvolves: "Floette-Eternal",
+		megaStone: { "Floette-Eternal": "Floette-Mega" },
 		itemUser: ["Floette-Eternal"],
 		onTakeItem(item, source) {
-			if ([item.megaEvolves, item.megaStone].includes(source.baseSpecies.name)) return false;
-			return true;
+			return !item.megaStone || (!item.megaStone[source.baseSpecies.name] &&
+				!Object.values(item.megaStone).includes(source.baseSpecies.name));
 		},
 		num: 2579,
 		gen: 9,
@@ -2397,12 +2328,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	froslassite: {
 		name: "Froslassite",
 		spritenum: 551,
-		megaStone: "Froslass-Mega",
-		megaEvolves: "Froslass",
+		megaStone: { "Froslass": "Froslass-Mega" },
 		itemUser: ["Froslass"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2566,
 		gen: 9,
@@ -2440,12 +2369,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	galladite: {
 		name: "Galladite",
 		spritenum: 616,
-		megaStone: "Gallade-Mega",
-		megaEvolves: "Gallade",
+		megaStone: { "Gallade": "Gallade-Mega" },
 		itemUser: ["Gallade"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 756,
 		gen: 6,
@@ -2474,12 +2401,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	garchompite: {
 		name: "Garchompite",
 		spritenum: 573,
-		megaStone: "Garchomp-Mega",
-		megaEvolves: "Garchomp",
+		megaStone: { "Garchomp": "Garchomp-Mega" },
 		itemUser: ["Garchomp"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 683,
 		gen: 6,
@@ -2488,12 +2413,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	garchompitez: {
 		name: "Garchompite Z",
 		spritenum: 573,
-		megaStone: "Garchomp-Mega-Z",
-		megaEvolves: "Garchomp",
+		megaStone: { "Garchomp": "Garchomp-Mega-Z" },
 		itemUser: ["Garchomp"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2590,
 		gen: 9,
@@ -2502,12 +2425,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	gardevoirite: {
 		name: "Gardevoirite",
 		spritenum: 587,
-		megaStone: "Gardevoir-Mega",
-		megaEvolves: "Gardevoir",
+		megaStone: { "Gardevoir": "Gardevoir-Mega" },
 		itemUser: ["Gardevoir"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 657,
 		gen: 6,
@@ -2516,12 +2437,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	gengarite: {
 		name: "Gengarite",
 		spritenum: 588,
-		megaStone: "Gengar-Mega",
-		megaEvolves: "Gengar",
+		megaStone: { "Gengar": "Gengar-Mega" },
 		itemUser: ["Gengar"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 656,
 		gen: 6,
@@ -2572,12 +2491,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	glalitite: {
 		name: "Glalitite",
 		spritenum: 623,
-		megaStone: "Glalie-Mega",
-		megaEvolves: "Glalie",
+		megaStone: { "Glalie": "Glalie-Mega" },
 		itemUser: ["Glalie"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 763,
 		gen: 6,
@@ -2586,12 +2503,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	glimmoranite: {
 		name: "Glimmoranite",
 		spritenum: 0,
-		megaStone: "Glimmora-Mega",
-		megaEvolves: "Glimmora",
+		megaStone: { "Glimmora": "Glimmora-Mega" },
 		itemUser: ["Glimmora"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2600,
 		gen: 9,
@@ -2609,12 +2524,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	golisopite: {
 		name: "Golisopite",
 		spritenum: 0,
-		megaStone: "Golisopod-Mega",
-		megaEvolves: "Golisopod",
+		megaStone: { "Golisopod": "Golisopod-Mega" },
 		itemUser: ["Golisopod"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2596,
 		gen: 9,
@@ -2623,12 +2536,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	golurkite: {
 		name: "Golurkite",
 		spritenum: 0,
-		megaStone: "Golurk-Mega",
-		megaEvolves: "Golurk",
+		megaStone: { "Golurk": "Golurk-Mega" },
 		itemUser: ["Golurk"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2594,
 		gen: 9,
@@ -2709,13 +2620,11 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	greninjite: {
 		name: "Greninjite",
 		spritenum: 560,
-		megaStone: "Greninja-Mega",
-		megaEvolves: "Greninja",
+		megaStone: { "Greninja": "Greninja-Mega" },
 		itemUser: ["Greninja"],
 		onTakeItem(item, source) {
 			// TODO: Figure out if this works on Greninja-Bond
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2577,
 		gen: 9,
@@ -2824,12 +2733,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	gyaradosite: {
 		name: "Gyaradosite",
 		spritenum: 589,
-		megaStone: "Gyarados-Mega",
-		megaEvolves: "Gyarados",
+		megaStone: { "Gyarados": "Gyarados-Mega" },
 		itemUser: ["Gyarados"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 676,
 		gen: 6,
@@ -2877,12 +2784,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	hawluchanite: {
 		name: "Hawluchanite",
 		spritenum: 566,
-		megaStone: "Hawlucha-Mega",
-		megaEvolves: "Hawlucha",
+		megaStone: { "Hawlucha": "Hawlucha-Mega" },
 		itemUser: ["Hawlucha"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2583,
 		gen: 9,
@@ -2919,12 +2824,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	heatranite: {
 		name: "Heatranite",
 		spritenum: 0,
-		megaStone: "Heatran-Mega",
-		megaEvolves: "Heatran",
+		megaStone: { "Heatran": "Heatran-Mega" },
 		itemUser: ["Heatran"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2592,
 		gen: 9,
@@ -2969,12 +2872,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	heracronite: {
 		name: "Heracronite",
 		spritenum: 590,
-		megaStone: "Heracross-Mega",
-		megaEvolves: "Heracross",
+		megaStone: { "Heracross": "Heracross-Mega" },
 		itemUser: ["Heracross"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 680,
 		gen: 6,
@@ -2995,12 +2896,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	houndoominite: {
 		name: "Houndoominite",
 		spritenum: 591,
-		megaStone: "Houndoom-Mega",
-		megaEvolves: "Houndoom",
+		megaStone: { "Houndoom": "Houndoom-Mega" },
 		itemUser: ["Houndoom"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 666,
 		gen: 6,
@@ -3213,12 +3112,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	kangaskhanite: {
 		name: "Kangaskhanite",
 		spritenum: 592,
-		megaStone: "Kangaskhan-Mega",
-		megaEvolves: "Kangaskhan",
+		megaStone: { "Kangaskhan": "Kangaskhan-Mega" },
 		itemUser: ["Kangaskhan"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 675,
 		gen: 6,
@@ -3371,12 +3268,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	latiasite: {
 		name: "Latiasite",
 		spritenum: 629,
-		megaStone: "Latias-Mega",
-		megaEvolves: "Latias",
+		megaStone: { "Latias": "Latias-Mega" },
 		itemUser: ["Latias"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 684,
 		gen: 6,
@@ -3385,12 +3280,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	latiosite: {
 		name: "Latiosite",
 		spritenum: 630,
-		megaStone: "Latios-Mega",
-		megaEvolves: "Latios",
+		megaStone: { "Latios": "Latios-Mega" },
 		itemUser: ["Latios"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 685,
 		gen: 6,
@@ -3571,12 +3464,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	lopunnite: {
 		name: "Lopunnite",
 		spritenum: 626,
-		megaStone: "Lopunny-Mega",
-		megaEvolves: "Lopunny",
+		megaStone: { "Lopunny": "Lopunny-Mega" },
 		itemUser: ["Lopunny"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 768,
 		gen: 6,
@@ -3601,12 +3492,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	lucarionite: {
 		name: "Lucarionite",
 		spritenum: 594,
-		megaStone: "Lucario-Mega",
-		megaEvolves: "Lucario",
+		megaStone: { "Lucario": "Lucario-Mega" },
 		itemUser: ["Lucario"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 673,
 		gen: 6,
@@ -3615,12 +3504,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	lucarionitez: {
 		name: "Lucarionite Z",
 		spritenum: 594,
-		megaStone: "Lucario-Mega-Z",
-		megaEvolves: "Lucario",
+		megaStone: { "Lucario": "Lucario-Mega-Z" },
 		itemUser: ["Lucario"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2591,
 		gen: 9,
@@ -3772,12 +3659,14 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	magearnite: {
 		name: "Magearnite",
 		spritenum: 0,
-		megaStone: ["Magearna-Mega", "Magearna-Original-Mega"],
-		megaEvolves: ["Magearna", "Magearna-Original"],
+		megaStone: {
+			"Magearna": "Magearna-Mega",
+			"Magearna-Original": "Magearna-Original-Mega",
+		},
 		itemUser: ["Magearna", "Magearna-Original"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves!.includes(source.baseSpecies.baseSpecies)) return false;
-			return true;
+			return !item.megaStone || (!item.megaStone[source.baseSpecies.name] &&
+				!Object.values(item.megaStone).includes(source.baseSpecies.name));
 		},
 		num: 2597,
 		gen: 9,
@@ -3860,12 +3749,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	malamarite: {
 		name: "Malamarite",
 		spritenum: 563,
-		megaStone: "Malamar-Mega",
-		megaEvolves: "Malamar",
+		megaStone: { "Malamar": "Malamar-Mega" },
 		itemUser: ["Malamar"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2580,
 		gen: 9,
@@ -3883,12 +3770,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	manectite: {
 		name: "Manectite",
 		spritenum: 596,
-		megaStone: "Manectric-Mega",
-		megaEvolves: "Manectric",
+		megaStone: { "Manectric": "Manectric-Mega" },
 		itemUser: ["Manectric"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 682,
 		gen: 6,
@@ -3943,12 +3828,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	mawilite: {
 		name: "Mawilite",
 		spritenum: 598,
-		megaStone: "Mawile-Mega",
-		megaEvolves: "Mawile",
+		megaStone: { "Mawile": "Mawile-Mega" },
 		itemUser: ["Mawile"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 681,
 		gen: 6,
@@ -3977,12 +3860,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	medichamite: {
 		name: "Medichamite",
 		spritenum: 599,
-		megaStone: "Medicham-Mega",
-		megaEvolves: "Medicham",
+		megaStone: { "Medicham": "Medicham-Mega" },
 		itemUser: ["Medicham"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 665,
 		gen: 6,
@@ -3991,12 +3872,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	meganiumite: {
 		name: "Meganiumite",
 		spritenum: 548,
-		megaStone: "Meganium-Mega",
-		megaEvolves: "Meganium",
+		megaStone: { "Meganium": "Meganium-Mega" },
 		itemUser: ["Meganium"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2563,
 		gen: 9,
@@ -4043,12 +3922,14 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	meowsticite: {
 		name: "Meowsticite",
 		spritenum: 0,
-		megaStone: ["Meowstic-M-Mega", "Meowstic-F-Mega"],
-		megaEvolves: ["Meowstic", "Meowstic-F"],
+		megaStone: {
+			"Meowstic": "Meowstic-M-Mega",
+			"Meowstic-F": "Meowstic-F-Mega",
+		},
 		itemUser: ["Meowstic", "Meowstic-F"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves!.includes(source.baseSpecies.baseSpecies)) return false;
-			return true;
+			return !item.megaStone || (!item.megaStone[source.baseSpecies.name] &&
+				!Object.values(item.megaStone).includes(source.baseSpecies.name));
 		},
 		num: 2594,
 		gen: 9,
@@ -4057,12 +3938,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	metagrossite: {
 		name: "Metagrossite",
 		spritenum: 618,
-		megaStone: "Metagross-Mega",
-		megaEvolves: "Metagross",
+		megaStone: { "Metagross": "Metagross-Mega" },
 		itemUser: ["Metagross"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 758,
 		gen: 6,
@@ -4164,12 +4043,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	mewtwonitex: {
 		name: "Mewtwonite X",
 		spritenum: 600,
-		megaStone: "Mewtwo-Mega-X",
-		megaEvolves: "Mewtwo",
+		megaStone: { "Mewtwo": "Mewtwo-Mega-X" },
 		itemUser: ["Mewtwo"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 662,
 		gen: 6,
@@ -4178,12 +4055,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	mewtwonitey: {
 		name: "Mewtwonite Y",
 		spritenum: 601,
-		megaStone: "Mewtwo-Mega-Y",
-		megaEvolves: "Mewtwo",
+		megaStone: { "Mewtwo": "Mewtwo-Mega-Y" },
 		itemUser: ["Mewtwo"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 663,
 		gen: 6,
@@ -4677,12 +4552,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	pidgeotite: {
 		name: "Pidgeotite",
 		spritenum: 622,
-		megaStone: "Pidgeot-Mega",
-		megaEvolves: "Pidgeot",
+		megaStone: { "Pidgeot": "Pidgeot-Mega" },
 		itemUser: ["Pidgeot"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 762,
 		gen: 6,
@@ -4726,12 +4599,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	pinsirite: {
 		name: "Pinsirite",
 		spritenum: 602,
-		megaStone: "Pinsir-Mega",
-		megaEvolves: "Pinsir",
+		megaStone: { "Pinsir": "Pinsir-Mega" },
 		itemUser: ["Pinsir"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 671,
 		gen: 6,
@@ -5082,12 +4953,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	pyroarite: {
 		name: "Pyroarite",
 		spritenum: 561,
-		megaStone: "Pyroar-Mega",
-		megaEvolves: "Pyroar",
+		megaStone: { "Pyroar": "Pyroar-Mega" },
 		itemUser: ["Pyroar"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2578,
 		gen: 9,
@@ -5161,13 +5030,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	raichunitex: {
 		name: "Raichunite X",
 		spritenum: 0,
-		megaStone: "Raichu-Mega-X",
-		megaEvolves: "Raichu",
+		megaStone: { "Raichu": "Raichu-Mega-X" },
 		itemUser: ["Raichu"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.name ||
-				item.megaStone === source.baseSpecies.name) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2585,
 		gen: 9,
@@ -5176,13 +5042,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	raichunitey: {
 		name: "Raichunite Y",
 		spritenum: 0,
-		megaStone: "Raichu-Mega-Y",
-		megaEvolves: "Raichu",
+		megaStone: { "Raichu": "Raichu-Mega-Y" },
 		itemUser: ["Raichu"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.name ||
-				item.megaStone === source.baseSpecies.name) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2586,
 		gen: 9,
@@ -5561,12 +5424,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	sablenite: {
 		name: "Sablenite",
 		spritenum: 614,
-		megaStone: "Sableye-Mega",
-		megaEvolves: "Sableye",
+		megaStone: { "Sableye": "Sableye-Mega" },
 		itemUser: ["Sableye"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 754,
 		gen: 6,
@@ -5640,12 +5501,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	salamencite: {
 		name: "Salamencite",
 		spritenum: 627,
-		megaStone: "Salamence-Mega",
-		megaEvolves: "Salamence",
+		megaStone: { "Salamence": "Salamence-Mega" },
 		itemUser: ["Salamence"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 769,
 		gen: 6,
@@ -5654,12 +5513,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	sceptilite: {
 		name: "Sceptilite",
 		spritenum: 613,
-		megaStone: "Sceptile-Mega",
-		megaEvolves: "Sceptile",
+		megaStone: { "Sceptile": "Sceptile-Mega" },
 		itemUser: ["Sceptile"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 753,
 		gen: 6,
@@ -5668,12 +5525,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	scizorite: {
 		name: "Scizorite",
 		spritenum: 605,
-		megaStone: "Scizor-Mega",
-		megaEvolves: "Scizor",
+		megaStone: { "Scizor": "Scizor-Mega" },
 		itemUser: ["Scizor"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 670,
 		gen: 6,
@@ -5682,12 +5537,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	scolipite: {
 		name: "Scolipite",
 		spritenum: 554,
-		megaStone: "Scolipede-Mega",
-		megaEvolves: "Scolipede",
+		megaStone: { "Scolipede": "Scolipede-Mega" },
 		itemUser: ["Scolipede"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2571,
 		gen: 9,
@@ -5708,12 +5561,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	scovillainite: {
 		name: "Scovillainite",
 		spritenum: 0,
-		megaStone: "Scovillain-Mega",
-		megaEvolves: "Scovillain",
+		megaStone: { "Scovillain": "Scovillain-Mega" },
 		itemUser: ["Scovillain"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2599,
 		gen: 9,
@@ -5722,12 +5573,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	scraftinite: {
 		name: "Scraftinite",
 		spritenum: 555,
-		megaStone: "Scrafty-Mega",
-		megaEvolves: "Scrafty",
+		megaStone: { "Scrafty": "Scrafty-Mega" },
 		itemUser: ["Scrafty"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2572,
 		gen: 9,
@@ -5767,12 +5616,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	sharpedonite: {
 		name: "Sharpedonite",
 		spritenum: 619,
-		megaStone: "Sharpedo-Mega",
-		megaEvolves: "Sharpedo",
+		megaStone: { "Sharpedo": "Sharpedo-Mega" },
 		itemUser: ["Sharpedo"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 759,
 		gen: 6,
@@ -5914,12 +5761,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	skarmorite: {
 		name: "Skarmorite",
 		spritenum: 550,
-		megaStone: "Skarmory-Mega",
-		megaEvolves: "Skarmory",
+		megaStone: { "Skarmory": "Skarmory-Mega" },
 		itemUser: ["Skarmory"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2565,
 		gen: 9,
@@ -5958,12 +5803,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	slowbronite: {
 		name: "Slowbronite",
 		spritenum: 620,
-		megaStone: "Slowbro-Mega",
-		megaEvolves: "Slowbro",
+		megaStone: { "Slowbro": "Slowbro-Mega" },
 		itemUser: ["Slowbro"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 760,
 		gen: 6,
@@ -6129,12 +5972,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	staraptite: {
 		name: "Staraptite",
 		spritenum: 0,
-		megaStone: "Staraptor-Mega",
-		megaEvolves: "Staraptor",
+		megaStone: { "Staraptor": "Staraptor-Mega" },
 		itemUser: ["Staraptor"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2589,
 		gen: 9,
@@ -6175,12 +6016,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	starminite: {
 		name: "Starminite",
 		spritenum: 546,
-		megaStone: "Starmie-Mega",
-		megaEvolves: "Starmie",
+		megaStone: { "Starmie": "Starmie-Mega" },
 		itemUser: ["Starmie"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2561,
 		gen: 9,
@@ -6224,12 +6063,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	steelixite: {
 		name: "Steelixite",
 		spritenum: 621,
-		megaStone: "Steelix-Mega",
-		megaEvolves: "Steelix",
+		megaStone: { "Steelix": "Steelix-Mega" },
 		itemUser: ["Steelix"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 761,
 		gen: 6,
@@ -6338,12 +6175,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	swampertite: {
 		name: "Swampertite",
 		spritenum: 612,
-		megaStone: "Swampert-Mega",
-		megaEvolves: "Swampert",
+		megaStone: { "Swampert": "Swampert-Mega" },
 		itemUser: ["Swampert"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 752,
 		gen: 6,
@@ -6426,12 +6261,15 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	tatsugirinite: {
 		name: "Tatsugirinite",
 		spritenum: 0,
-		megaStone: ["Tatsugiri-Curly-Mega", "Tatsugiri-Droopy-Mega", "Tatsugiri-Stretchy-Mega"],
-		megaEvolves: ["Tatsugiri", "Tatsugiri-Droopy", "Tatsugiri-Stretchy"],
+		megaStone: {
+			"Tatsugiri": "Tatsugiri-Curly-Mega",
+			"Tatsugiri-Droopy": "Tatsugiri-Droopy-Mega",
+			"Tatsugiri-Stretchy": "Tatsugiri-Stretchy-Mega",
+		},
 		itemUser: ["Tatsugiri", "Tatsugiri-Droopy", "Tatsugiri-Stretchy"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves!.includes(source.baseSpecies.baseSpecies)) return false;
-			return true;
+			return !item.megaStone || (!item.megaStone[source.baseSpecies.name] &&
+				!Object.values(item.megaStone).includes(source.baseSpecies.name));
 		},
 		num: 2601,
 		gen: 9,
@@ -7549,12 +7387,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	tyranitarite: {
 		name: "Tyranitarite",
 		spritenum: 607,
-		megaStone: "Tyranitar-Mega",
-		megaEvolves: "Tyranitar",
+		megaStone: { "Tyranitar": "Tyranitar-Mega" },
 		itemUser: ["Tyranitar"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 669,
 		gen: 6,
@@ -7628,12 +7464,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	venusaurite: {
 		name: "Venusaurite",
 		spritenum: 608,
-		megaStone: "Venusaur-Mega",
-		megaEvolves: "Venusaur",
+		megaStone: { "Venusaur": "Venusaur-Mega" },
 		itemUser: ["Venusaur"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 659,
 		gen: 6,
@@ -7642,12 +7476,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	victreebelite: {
 		name: "Victreebelite",
 		spritenum: 545,
-		megaStone: "Victreebel-Mega",
-		megaEvolves: "Victreebel",
+		megaStone: { "Victreebel": "Victreebel-Mega" },
 		itemUser: ["Victreebel"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2560,
 		gen: 9,
@@ -7976,12 +7808,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	zeraorite: {
 		name: "Zeraorite",
 		spritenum: 0,
-		megaStone: "Zeraora-Mega",
-		megaEvolves: "Zeraora",
+		megaStone: { "Zeraora": "Zeraora-Mega" },
 		itemUser: ["Zeraora"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: 2598,
 		gen: 9,
@@ -8006,12 +7836,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	zygardite: {
 		name: "Zygardite",
 		spritenum: 568,
-		megaStone: "Zygarde-Mega",
-		megaEvolves: "Zygarde-Complete",
+		megaStone: { "Zygarde-Complete": "Zygarde-Mega" },
 		itemUser: ["Zygarde-Complete"],
 		onTakeItem(item, source) {
-			if (source.baseSpecies.baseSpecies === 'Zygarde') return false;
-			return true;
+			return source.baseSpecies.baseSpecies !== 'Zygarde';
 		},
 		num: 2584,
 		gen: 9,
@@ -8303,12 +8131,10 @@ export const Items: import('../sim/dex-items').ItemDataTable = {
 	crucibellite: {
 		name: "Crucibellite",
 		spritenum: 577,
-		megaStone: "Crucibelle-Mega",
-		megaEvolves: "Crucibelle",
+		megaStone: { "Crucibelle": "Crucibelle-Mega" },
 		itemUser: ["Crucibelle"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: -1,
 		gen: 6,
diff --git a/data/mods/chatbats/items.ts b/data/mods/chatbats/items.ts
index d665b92d55e27..f0591805956b3 100644
--- a/data/mods/chatbats/items.ts
+++ b/data/mods/chatbats/items.ts
@@ -13,12 +13,10 @@ export const Items: import('../../../sim/dex-items').ModdedItemDataTable = {
 	masquerainite: {
 		name: "Masquerainite",
 		spritenum: 1,
-		megaStone: "Masquerain-Mega",
-		megaEvolves: "Masquerain",
+		megaStone: { "Masquerain": "Masquerain-Mega" },
 		itemUser: ["Masquerain"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: -1,
 		gen: 9,
@@ -59,12 +57,10 @@ export const Items: import('../../../sim/dex-items').ModdedItemDataTable = {
 	typhlosionite: {
 		name: "Typhlosionite",
 		spritenum: 1,
-		megaStone: "Typhlosion-Mega",
-		megaEvolves: "Typhlosion",
+		megaStone: { "Typhlosion": "Typhlosion-Mega" },
 		itemUser: ["Typhlosion"],
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		num: -2,
 		gen: 9,
diff --git a/data/mods/gen8/rulesets.ts b/data/mods/gen8/rulesets.ts
index 7958555ccaa50..866c2568da322 100644
--- a/data/mods/gen8/rulesets.ts
+++ b/data/mods/gen8/rulesets.ts
@@ -92,10 +92,10 @@ export const Rulesets: import('../../../sim/dex-formats').ModdedFormatDataTable
 				if (["Zacian", "Zamazenta"].includes(species.baseSpecies) && this.toID(set.item).startsWith('rusted')) {
 					species = this.dex.species.get(set.species + "-Crowned");
 				}
-				if (set.item && this.dex.items.get(set.item).megaStone) {
+				if (set.item) {
 					const item = this.dex.items.get(set.item);
-					if (item.megaEvolves === species.baseSpecies) {
-						species = this.dex.species.get(Array.isArray(item.megaStone) ? item.megaStone[0] : item.megaStone);
+					if (item.megaStone?.[species.baseSpecies]) {
+						species = this.dex.species.get(item.megaStone[species.baseSpecies]);
 					}
 				}
 				if (
@@ -123,8 +123,8 @@ export const Rulesets: import('../../../sim/dex-formats').ModdedFormatDataTable
 				}
 				if (set.item) {
 					const item = this.dex.items.get(set.item);
-					if (item.megaEvolves === set.species) {
-						godSpecies = this.dex.species.get(Array.isArray(item.megaStone) ? item.megaStone[0] : item.megaStone);
+					if (item.megaStone?.[set.species]) {
+						godSpecies = this.dex.species.get(item.megaStone[set.species]);
 					}
 					if (["Zacian", "Zamazenta"].includes(godSpecies.baseSpecies) && item.id.startsWith('rusted')) {
 						godSpecies = this.dex.species.get(set.species + "-Crowned");
diff --git a/data/mods/gen9legendsou/items.ts b/data/mods/gen9legendsou/items.ts
index 5a4e3fb9c0fc5..9e71c2e5cbcd8 100644
--- a/data/mods/gen9legendsou/items.ts
+++ b/data/mods/gen9legendsou/items.ts
@@ -2,15 +2,15 @@ export const Items: import('../../../sim/dex-items').ModdedItemDataTable = {
 	slowbronite: {
 		inherit: true,
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.name || item.megaStone === source.baseSpecies.name) return false;
-			return true;
+			return !item.megaStone || (!item.megaStone[source.baseSpecies.name] &&
+				!Object.values(item.megaStone).includes(source.baseSpecies.name));
 		},
 	},
 	greninjite: {
 		inherit: true,
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.name || item.megaStone === source.baseSpecies.name) return false;
-			return true;
+			return !item.megaStone || (!item.megaStone[source.baseSpecies.name] &&
+				!Object.values(item.megaStone).includes(source.baseSpecies.name));
 		},
 	},
 	zygardite: {
diff --git a/data/mods/gen9legendsou/scripts.ts b/data/mods/gen9legendsou/scripts.ts
index a71a40b244517..ac0cdf8b940c6 100644
--- a/data/mods/gen9legendsou/scripts.ts
+++ b/data/mods/gen9legendsou/scripts.ts
@@ -57,23 +57,8 @@ export const Scripts: ModdedBattleScriptsData = {
 				pokemon.baseMoves.includes(this.battle.toID(altForme.requiredMove)) && !item.zMove) {
 				return altForme.name;
 			}
-			if (Array.isArray(item.megaEvolves)) {
-				if (!Array.isArray(item.megaStone)) {
-					throw new Error(`${item.name}#megaEvolves and ${item.name}#megaStone type mismatch`);
-				}
-				if (item.megaEvolves.length !== item.megaStone.length) {
-					throw new Error(`${item.name}#megaEvolves and ${item.name}#megaStone length mismatch`);
-				}
-				const index = item.megaEvolves.indexOf(species.name);
-				if (index < 0) return null;
-				return item.megaStone[index];
-			} else {
-				if (item.megaEvolves === species.name) {
-					if (Array.isArray(item.megaStone)) throw new Error(`${item.name}#megaEvolves and ${item.name}#megaStone type mismatch`);
-					return item.megaStone;
-				}
-			}
-			return null;
+			if (!item.megaStone) return null;
+			return item.megaStone[species.name];
 		},
 		runMegaEvo(pokemon) {
 			const speciesid = pokemon.canMegaEvo || pokemon.canUltraBurst;
diff --git a/data/mods/gen9ssb/items.ts b/data/mods/gen9ssb/items.ts
index ba538d227f084..db1bfae705a17 100644
--- a/data/mods/gen9ssb/items.ts
+++ b/data/mods/gen9ssb/items.ts
@@ -14,11 +14,9 @@ export const Items: import('../../../sim/dex-items').ModdedItemDataTable = {
 		name: "Flygonite",
 		spritenum: 111,
 		itemUser: ["Flygon"],
-		megaEvolves: "Flygon",
-		megaStone: "Trapinch",
+		megaStone: { "Trapinch": "Flygon" },
 		onTakeItem(item, source) {
-			if (item.megaEvolves === source.baseSpecies.baseSpecies) return false;
-			return true;
+			return !item.megaStone?.[source.baseSpecies.baseSpecies];
 		},
 		desc: "If held by a Flygon, this item allows it to Mega Evolve in battle.",
 	},
@@ -36,7 +34,7 @@ export const Items: import('../../../sim/dex-items').ModdedItemDataTable = {
 	gardevoirite: {
 		inherit: true,
 		itemUser: ["Ralts"],
-		megaEvolves: "Ralts",
+		megaStone: { "Ralts": "Gardevoir-Mega" },
 		desc: "If held by a Ralts, this item allows it to Mega Evolve in battle.",
 	},
 	// Peary
diff --git a/data/mods/gen9ssb/scripts.ts b/data/mods/gen9ssb/scripts.ts
index f1b3cbba00fb3..6be6a31470bd6 100644
--- a/data/mods/gen9ssb/scripts.ts
+++ b/data/mods/gen9ssb/scripts.ts
@@ -963,26 +963,11 @@ export const Scripts: ModdedBattleScriptsData = {
 				pokemon.baseMoves.includes(this.battle.toID(altForme.requiredMove)) && !item.zMove) {
 				return altForme.name;
 			}
+			if (!item.megaStone) return null;
 			// a hacked-in Megazard X can mega evolve into Megazard Y, but not into Megazard X
-			if (Array.isArray(item.megaEvolves)) {
-				if (!Array.isArray(item.megaStone)) {
-					throw new Error(`${item.name}#megaEvolves and ${item.name}#megaStone type mismatch`);
-				}
-				if (item.megaEvolves.length !== item.megaStone.length) {
-					throw new Error(`${item.name}#megaEvolves and ${item.name}#megaStone length mismatch`);
-				}
-				// FIXME: Change to species.name when champions comes
-				const index = item.megaEvolves.indexOf(species.baseSpecies);
-				if (index < 0) return null;
-				return item.megaStone[index];
-				// FIXME: Change to species.name when champions comes
-			} else {
-				if (item.megaEvolves === species.baseSpecies) {
-					if (Array.isArray(item.megaStone)) throw new Error(`${item.name}#megaEvolves and ${item.name}#megaStone type mismatch`);
-					return item.megaStone;
-				}
-			}
-			return null;
+			// FIXME: Change to species.name when champions comes
+			const megaEvolution = item.megaStone[species.baseSpecies];
+			return megaEvolution && megaEvolution !== species.name ? megaEvolution : null;
 		},
 
 		// 1 Z per pokemon
diff --git a/data/mods/mixandmega/scripts.ts b/data/mods/mixandmega/scripts.ts
index 78d85cce0b89c..77089a00c4503 100644
--- a/data/mods/mixandmega/scripts.ts
+++ b/data/mods/mixandmega/scripts.ts
@@ -385,12 +385,8 @@ export const Scripts: ModdedBattleScriptsData = {
 			if (pokemon.species.isMega) return null;
 
 			const item = pokemon.getItem();
-			if (item.megaStone) {
-				if (item.megaStone.includes(pokemon.baseSpecies.name)) return null;
-				return Array.isArray(item.megaStone) ? item.megaStone[0] : item.megaStone;
-			} else {
-				return null;
-			}
+			if (!item.megaStone || item.megaStone[pokemon.baseSpecies.name]) return null;
+			return Object.values(item.megaStone)[0];
 		},
 		runMegaEvo(pokemon) {
 			if (pokemon.species.isMega) return false;
diff --git a/data/random-battles/gen7/teams.ts b/data/random-battles/gen7/teams.ts
index 1f427d5304d4f..3f6278ca554d8 100644
--- a/data/random-battles/gen7/teams.ts
+++ b/data/random-battles/gen7/teams.ts
@@ -1607,8 +1607,7 @@ export class RandomGen7Teams extends RandomGen8Teams {
 			if (isMonotype) {
 				// Prevents Mega Evolutions from breaking the type limits
 				if (itemData.megaStone) {
-					const megaSpecies = this.dex.species.get(Array.isArray(itemData.megaStone) ?
-						itemData.megaStone[0] : itemData.megaStone);
+					const megaSpecies = this.dex.species.get(Object.values(itemData.megaStone)[0]);
 					if (types.length > megaSpecies.types.length) types = [species.types[0]];
 					// Only check the second type because a Mega Evolution should always share the first type with its base forme.
 					if (megaSpecies.types[1] && types[1] && megaSpecies.types[1] !== types[1]) {
diff --git a/data/rulesets.ts b/data/rulesets.ts
index f051d043f3266..d3d6f68b634db 100644
--- a/data/rulesets.ts
+++ b/data/rulesets.ts
@@ -1507,17 +1507,9 @@ export const Rulesets: import('../sim/dex-formats').FormatDataTable = {
 					typeTable = typeTable.filter(type => species.types.includes(type));
 				}
 				const item = this.dex.items.get(set.item);
-				if (item.megaStone) {
-					if (Array.isArray(item.megaStone)) {
-						const index = (item.megaEvolves as string[]).indexOf(species.name);
-						if (index >= 0) {
-							species = this.dex.species.get(item.megaStone[index]);
-							typeTable = typeTable.filter(type => species.types.includes(type));
-						}
-					} else {
-						species = this.dex.species.get(item.megaStone);
-						typeTable = typeTable.filter(type => species.types.includes(type));
-					}
+				if (item.megaStone?.[species.name]) {
+					species = this.dex.species.get(item.megaStone[species.name]);
+					typeTable = typeTable.filter(type => species.types.includes(type));
 				}
 				if (item.id === "ultranecroziumz" && species.baseSpecies === "Necrozma") {
 					species = this.dex.species.get("Necrozma-Ultra");
@@ -1556,17 +1548,9 @@ export const Rulesets: import('../sim/dex-formats').FormatDataTable = {
 				}
 				color = species.color;
 				const item = this.dex.items.get(set.item);
-				if (item.megaStone) {
-					if (Array.isArray(item.megaStone)) {
-						const index = (item.megaEvolves as string[]).indexOf(species.name);
-						if (index >= 0) {
-							species = this.dex.species.get(item.megaStone[index]);
-							color = species.color;
-						}
-					} else {
-						species = this.dex.species.get(item.megaStone);
-						color = species.color;
-					}
+				if (item.megaStone?.[species.name]) {
+					species = this.dex.species.get(item.megaStone[species.name]);
+					color = species.color;
 				}
 				if (item.id === "ultranecroziumz" && species.baseSpecies === "Necrozma") {
 					species = this.dex.species.get("Necrozma-Ultra");
@@ -2666,12 +2650,10 @@ export const Rulesets: import('../sim/dex-formats').FormatDataTable = {
 				) {
 					species = this.dex.species.get(`${species.baseSpecies}-Crowned`);
 				}
-				if (set.item && this.dex.items.get(set.item).megaStone) {
+				if (set.item) {
 					const item = this.dex.items.get(set.item);
-					if (item.megaEvolves?.includes(species.name)) {
-						species = this.dex.species.get(Array.isArray(item.megaEvolves) ?
-							(item.megaStone as string[])[item.megaEvolves.indexOf(species.name)] :
-							item.megaStone as string);
+					if (item.megaStone?.[species.name]) {
+						species = this.dex.species.get(item.megaStone[species.name]);
 					}
 				}
 				if (this.ruleTable.isRestrictedSpecies(species) ||
@@ -2693,10 +2675,8 @@ export const Rulesets: import('../sim/dex-formats').FormatDataTable = {
 				}
 				if (set.item) {
 					const item = this.dex.items.get(set.item);
-					if (item.megaEvolves?.includes(set.species)) {
-						godSpecies = this.dex.species.get(Array.isArray(item.megaEvolves) ?
-							(item.megaStone as string[])[item.megaEvolves.indexOf(set.species)] :
-							item.megaStone as string);
+					if (item.megaStone?.[set.species]) {
+						godSpecies = this.dex.species.get(item.megaStone[set.species]);
 					}
 					if (["Zacian", "Zamazenta"].includes(godSpecies.baseSpecies) && item.id.startsWith('rusted')) {
 						godSpecies = this.dex.species.get(set.species + "-Crowned");
diff --git a/server/chat-plugins/othermetas.ts b/server/chat-plugins/othermetas.ts
index fd356b3cd5c37..37a54c70d4021 100644
--- a/server/chat-plugins/othermetas.ts
+++ b/server/chat-plugins/othermetas.ts
@@ -29,14 +29,23 @@ function getMegaStone(stone: string, mod = 'gen9'): Item | null {
 				id: move.id,
 				name: move.name,
 				fullname: move.name,
-				megaEvolves: 'Rayquaza',
-				megaStone: 'Rayquaza-Mega',
+				megaStone: { 'Rayquaza': 'Rayquaza-Mega' },
 				exists: true,
 				// Adding extra values to appease typescript
 				gen: 6,
 				num: -1,
 				effectType: 'Item',
 				sourceEffect: '',
+				isBerry: false,
+				ignoreKlutz: false,
+				isGem: false,
+				isPokeball: false,
+				isPrimalOrb: false,
+				shortDesc: "",
+				desc: "",
+				isNonstandard: null,
+				noCopy: false,
+				affectsFainted: false,
 			} as Item;
 		} else {
 			return null;
@@ -131,8 +140,8 @@ export const commands: Chat.ChatCommands = {
 				megaSpecies = dex.species.get(forcedForme);
 				baseSpecies = dex.species.get(forcedForme.split('-')[0]);
 			} else {
-				megaSpecies = dex.species.get(Array.isArray(stone.megaStone) ? stone.megaStone[0] : stone.megaStone);
-				baseSpecies = dex.species.get(Array.isArray(stone.megaEvolves) ? stone.megaEvolves[0] : stone.megaEvolves);
+				megaSpecies = dex.species.get(Object.values(stone.megaStone!)[0]);
+				baseSpecies = dex.species.get(Object.keys(stone.megaStone!)[0]);
 			}
 			break;
 		}
@@ -282,8 +291,8 @@ export const commands: Chat.ChatCommands = {
 					megaSpecies = dex.species.get(forcedForme);
 					baseSpecies = dex.species.get(forcedForme.split('-')[0]);
 				} else {
-					megaSpecies = dex.species.get(Array.isArray(aStone.megaStone) ? aStone.megaStone[0] : aStone.megaStone);
-					baseSpecies = dex.species.get(Array.isArray(aStone.megaEvolves) ? aStone.megaEvolves[0] : aStone.megaEvolves);
+					megaSpecies = dex.species.get(Object.values(aStone.megaStone!)[0]);
+					baseSpecies = dex.species.get(Object.keys(aStone.megaStone!)[0]);
 				}
 				break;
 			}
diff --git a/server/chat-plugins/randombattles/ssb.tsx b/server/chat-plugins/randombattles/ssb.tsx
index 5f7df25a44535..10d2f329d3866 100644
--- a/server/chat-plugins/randombattles/ssb.tsx
+++ b/server/chat-plugins/randombattles/ssb.tsx
@@ -373,7 +373,7 @@ class SSBSetsHTML extends Chat.JSX.Component<{ target: string }> {
 			<SSBInnateHTML name={setName} dex={dex} baseDex={baseDex} />
 			<SSBPokemonHTML species={set.species} dex={dex} baseDex={baseDex} />
 			{(!Array.isArray(set.item) && item.megaStone) && <SSBPokemonHTML
-				species={Array.isArray(item.megaStone) ? item.megaStone[0] : item.megaStone} dex={dex} baseDex={baseDex}
+				species={Object.values(item.megaStone)[0]} dex={dex} baseDex={baseDex}
 			/>}
 			{/* keys and Kennedy have an itemless forme change */}
 			{['Rayquaza'].includes(set.species) && <SSBPokemonHTML species={`${set.species}-Mega`} dex={dex} baseDex={baseDex} />}
diff --git a/server/chat-plugins/randombattles/winrates.tsx b/server/chat-plugins/randombattles/winrates.tsx
index cbba1ce0a4472..f61e95652f5d9 100644
--- a/server/chat-plugins/randombattles/winrates.tsx
+++ b/server/chat-plugins/randombattles/winrates.tsx
@@ -134,7 +134,7 @@ export function getSpeciesName(set: PokemonSet, format: Format) {
 	} else if (species === "Groudon" && item.name === "Red Orb") {
 		return "Groudon-Primal";
 	} else if (item.megaStone) {
-		return Array.isArray(item.megaStone) ? item.megaStone[0] : item.megaStone;
+		return Object.values(item.megaStone)[0];
 	} else if (species === "Rayquaza" && moves.includes('Dragon Ascent') && !item.zMove && megaRayquazaPossible) {
 		return "Rayquaza-Mega";
 	} else if (species === "Poltchageist-Artisan") { // Babymons from here on out
diff --git a/sim/battle-actions.ts b/sim/battle-actions.ts
index 55243f4f23557..7879fdd6c0205 100644
--- a/sim/battle-actions.ts
+++ b/sim/battle-actions.ts
@@ -1871,21 +1871,15 @@ export class BattleActions {
 			pokemon.baseMoves.includes(toID(altForme.requiredMove)) && !item.zMove) {
 			return altForme.name;
 		}
+		if (!item.megaStone) return null;
 		// Temporary hardcode until generation shift
-		if ((species.baseSpecies === "Floette" || species.baseSpecies === "Zygarde") && item.megaEvolves === species.name) {
-			return item.megaStone as string;
+		if ((species.baseSpecies === "Floette" || species.baseSpecies === "Zygarde") && item.megaStone[species.name]) {
+			return item.megaStone[species.name];
 		}
 		// a hacked-in Megazard X can mega evolve into Megazard Y, but not into Megazard X
-		if (Array.isArray(item.megaStone)) {
-			// FIXME: Change to species.name when champions comes
-			const index = (item.megaEvolves as string[]).indexOf(species.baseSpecies);
-			if (index < 0) return null;
-			return item.megaStone[index];
-			// FIXME: Change to species.name when champions comes
-		} else if (item.megaEvolves === species.baseSpecies && item.megaStone !== species.name) {
-			return item.megaStone;
-		}
-		return null;
+		// FIXME: Change to species.name when champions comes
+		const megaEvolution = item.megaStone[species.baseSpecies];
+		return megaEvolution && megaEvolution !== species.name ? megaEvolution : null;
 	}
 
 	canUltraBurst(pokemon: Pokemon) {
diff --git a/sim/dex-abilities.ts b/sim/dex-abilities.ts
index 63e406cc52996..c3af1b2ccf1ab 100644
--- a/sim/dex-abilities.ts
+++ b/sim/dex-abilities.ts
@@ -85,7 +85,7 @@ export class DexAbilities {
 	}
 
 	getByID(id: ID): Ability {
-		if (id === '') return EMPTY_ABILITY;
+		if (id === '' || id === 'constructor') return EMPTY_ABILITY;
 		let ability = this.abilityCache.get(id);
 		if (ability) return ability;
 
diff --git a/sim/dex-conditions.ts b/sim/dex-conditions.ts
index 990ce7cd939be..057d6f3284955 100644
--- a/sim/dex-conditions.ts
+++ b/sim/dex-conditions.ts
@@ -665,7 +665,7 @@ export class DexConditions {
 	}
 
 	getByID(id: ID): Condition {
-		if (id === '') return EMPTY_CONDITION;
+		if (id === '' || id === 'constructor') return EMPTY_CONDITION;
 
 		let condition = this.conditionCache.get(id);
 		if (condition) return condition;
diff --git a/sim/dex-data.ts b/sim/dex-data.ts
index 59c505737c338..55c47238a786a 100644
--- a/sim/dex-data.ts
+++ b/sim/dex-data.ts
@@ -172,7 +172,7 @@ export class DexNatures {
 		return this.getByID(toID(name));
 	}
 	getByID(id: ID): Nature {
-		if (id === '') return EMPTY_NATURE;
+		if (id === '' || id === 'constructor') return EMPTY_NATURE;
 		let nature = this.natureCache.get(id);
 		if (nature) return nature;
 
@@ -293,7 +293,7 @@ export class DexTypes {
 	}
 
 	getByID(id: ID): TypeInfo {
-		if (id === '') return EMPTY_TYPE_INFO;
+		if (id === '' || id === 'constructor') return EMPTY_TYPE_INFO;
 		let type = this.typeCache.get(id);
 		if (type) return type;
 
diff --git a/sim/dex-items.ts b/sim/dex-items.ts
index ef97fd8f43349..d8558177e7855 100644
--- a/sim/dex-items.ts
+++ b/sim/dex-items.ts
@@ -43,17 +43,11 @@ export class Item extends BasicEffect implements Readonly<BasicEffect> {
 	 */
 	readonly onMemory?: string;
 	/**
-	 * If this is a mega stone: The name (e.g. Charizard-Mega-X) of the
-	 * forme this allows transformation into.
+	 * If this is a mega stone: A pair (e.g. Charizard: Charizard-Mega-X) of the
+	 * forme this allows transformation from and into.
 	 * undefined, if not a mega stone.
 	 */
-	readonly megaStone?: string | string[];
-	/**
-	 * If this is a mega stone: The name (e.g. Charizard) of the
-	 * forme this allows transformation from.
-	 * undefined, if not a mega stone.
-	 */
-	readonly megaEvolves?: string | string[];
+	readonly megaStone?: { [megaEvolves: string]: string };
 	/**
 	 * If this is a Z crystal: true if the Z Crystal is generic
 	 * (e.g. Firium Z). If species-specific, the name
@@ -116,7 +110,6 @@ export class Item extends BasicEffect implements Readonly<BasicEffect> {
 		this.onDrive = data.onDrive || undefined;
 		this.onMemory = data.onMemory || undefined;
 		this.megaStone = data.megaStone || undefined;
-		this.megaEvolves = data.megaEvolves || undefined;
 		this.zMove = data.zMove || undefined;
 		this.zMoveType = data.zMoveType || undefined;
 		this.zMoveFrom = data.zMoveFrom || undefined;
@@ -176,7 +169,7 @@ export class DexItems {
 	}
 
 	getByID(id: ID): Item {
-		if (id === '') return EMPTY_ITEM;
+		if (id === '' || id === 'constructor') return EMPTY_ITEM;
 		let item = this.itemCache.get(id);
 		if (item) return item;
 		if (this.dex.getAlias(id)) {
diff --git a/sim/dex-moves.ts b/sim/dex-moves.ts
index 63f9a13afa73b..5b56490430382 100644
--- a/sim/dex-moves.ts
+++ b/sim/dex-moves.ts
@@ -621,7 +621,7 @@ export class DexMoves {
 	}
 
 	getByID(id: ID): Move {
-		if (id === '') return EMPTY_MOVE;
+		if (id === '' || id === 'constructor') return EMPTY_MOVE;
 		let move = this.moveCache.get(id);
 		if (move) return move;
 		if (this.dex.getAlias(id)) {
diff --git a/sim/dex-species.ts b/sim/dex-species.ts
index fab61861ca421..4a05d4ca0cf9c 100644
--- a/sim/dex-species.ts
+++ b/sim/dex-species.ts
@@ -436,7 +436,7 @@ export class DexSpecies {
 	}
 
 	getByID(id: ID): Species {
-		if (id === '') return EMPTY_SPECIES;
+		if (id === '' || id === 'constructor') return EMPTY_SPECIES;
 		let species: Mutable<Species> | undefined = this.speciesCache.get(id);
 		if (species) return species;
 
diff --git a/sim/team-validator.ts b/sim/team-validator.ts
index 8d234a9ea7705..e109837780ed3 100644
--- a/sim/team-validator.ts
+++ b/sim/team-validator.ts
@@ -526,14 +526,8 @@ export class TeamValidator {
 
 		if (ruleTable.has('obtainableformes')) {
 			const canMegaEvo = dex.gen <= 7 || ruleTable.has('+pokemontag:past');
-			if (item.megaEvolves?.includes(species.name)) {
-				if (!item.megaStone) throw new Error(`Item ${item.name} has no base form for mega evolution`);
-				if (Array.isArray(item.megaEvolves)) {
-					const idx = item.megaEvolves.indexOf(species.name);
-					tierSpecies = dex.species.get(item.megaStone[idx]);
-				} else {
-					tierSpecies = dex.species.get(item.megaStone as string);
-				}
+			if (item.megaStone?.[species.name]) {
+				tierSpecies = dex.species.get(item.megaStone[species.name]);
 			} else if (item.id === 'redorb' && species.id === 'groudon') {
 				tierSpecies = dex.species.get('Groudon-Primal');
 			} else if (item.id === 'blueorb' && species.id === 'kyogre') {
diff --git a/sim/tools/exhaustive-runner.ts b/sim/tools/exhaustive-runner.ts
index db239828ae01f..90cdecad5433c 100644
--- a/sim/tools/exhaustive-runner.ts
+++ b/sim/tools/exhaustive-runner.ts
@@ -137,8 +137,8 @@ export class ExhaustiveRunner {
 		const signatures = new Map();
 		for (const id of pools.items.possible) {
 			const item = dex.data.Items[id];
-			if (item.megaEvolves) {
-				const pokemon = toID(item.megaEvolves);
+			if (item.megaStone) {
+				const pokemon = toID(Object.keys(item.megaStone)[0]);
 				const combo = { item: id };
 				let combos = signatures.get(pokemon);
 				if (!combos) {
diff --git a/test/sim/data.js b/test/sim/data.js
index dcae534243477..9c8f96a2c58e0 100644
--- a/test/sim/data.js
+++ b/test/sim/data.js
@@ -132,12 +132,6 @@ describe('Dex data', () => {
 			const entry = Items[itemid];
 			assert.equal(toID(entry.name), itemid, `Mismatched Item key "${itemid}" of "${entry.name}"`);
 			assert.equal(typeof entry.num, 'number', `Item ${entry.name} should have a number`);
-			if (entry.megaStone) {
-				assert.equal(typeof entry.megaStone, typeof entry.megaEvolves, `Item ${entry.name} megaStone and megaEvolves should both be the same type`);
-				if (Array.isArray(entry.megaStone)) {
-					assert.equal(entry.megaStone.length, entry.megaEvolves.length, `Item ${entry.name} megaStone and megaEvolves arrays should be the same length`);
-				}
-			}
 		}
 	});
 
diff --git a/tools/set-import/importer.ts b/tools/set-import/importer.ts
index 9458ad0d7f35f..ab59d11bd2520 100644
--- a/tools/set-import/importer.ts
+++ b/tools/set-import/importer.ts
@@ -312,7 +312,8 @@ function skip(dex: ModdedDex, format: Format, pokemon: string, set: DeepPartial<
 		if (pokemon === 'Rayquaza-Mega') {
 			return format.id.includes('ubers') || !hasMove('Dragon Ascent');
 		} else {
-			return dex.items.get(set.item).megaStone !== pokemon;
+			const item = dex.items.get(set.item);
+			return !item.megaStone || !Object.values(item.megaStone).includes(pokemon);
 		}
 	}
 	if (pokemon === 'Necrozma-Ultra' && set.item !== 'Ultranecrozium Z') return true;