diff --git a/src/data/balance/trainers/trainer-party-configs.ts b/src/data/balance/trainers/trainer-party-configs.ts
index 28436e59ff9..d12f43f5a51 100644
--- a/src/data/balance/trainers/trainer-party-configs.ts
+++ b/src/data/balance/trainers/trainer-party-configs.ts
@@ -13,17 +13,16 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
       species: Species.DEWGONG,
       abilityIndex: 0, // Thick Fat
     }],
-    [2, [{
-      species: Species.SLOWBRO,
-      teraType: PokemonType.ICE,
-      instantTera: true,
-      presetMoves: [Moves.ICE_BEAM],
-    }, {
-      species: Species.GALAR_SLOWBRO,
-      teraType: PokemonType.ICE,
-      instantTera: true,
-      presetMoves: [Moves.ICE_BEAM],
-    }]],
+    [2, [
+      {species: Species.SLOWBRO},
+      {species: Species.GALAR_SLOWBRO}
+      ],
+      {
+        teraType: PokemonType.ICE,
+        instantTera: true,
+        presetMoves: [Moves.ICE_BEAM],
+      }
+    ],
     [3, { species: Species.JYNX }],
     [4, [{ species: Species.CLOYSTER }, { species: Species.ALOLA_SANDSLASH }]],
     [5, { species: Species.LAPRAS }]
@@ -47,16 +46,14 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [2, [{
       species: Species.ARBOK,
       abilityIndex: 0,
-      teraType: PokemonType.GHOST,
-      instantTera: true,
-      presetMoves: [Moves.TERA_BLAST],
-    }, {
+      }, {
       species: Species.WEEZING,
       abilityIndex: 0,
+    }], {
       teraType: PokemonType.GHOST,
       instantTera: true,
       presetMoves: [Moves.TERA_BLAST],
-    }]],
+    }],
     [3, { species: Species.ALOLA_MAROWAK }],
     [4, { species: Species.CURSOLA }],
     [5, {
@@ -68,15 +65,11 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [2, [{
       species: Species.GYARADOS,
       presetMoves: [Moves.SCALE_SHOT],
-      teraType: PokemonType.DRAGON,
-      instantTera: true,
     },
     {
       species: Species.AERODACTYL,
       presetMoves: [Moves.DRAGON_CLAW],
-      teraType: PokemonType.DRAGON,
-      instantTera: true,
-    }]
+    }], {instantTera: true}
     ],
     [3, { species: Species.ALOLA_EXEGGUTOR }],
     [4, { species: Species.SALAMENCE }],
@@ -85,19 +78,16 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
 
   [TrainerType.WILL]: [
     [0, { species: Species.JYNX }],
-    [2, [{
-      species: Species.SLOWKING,
+    [2, [
+      {species: Species.SLOWKING},
+      {species: Species.GALAR_SLOWKING},
+    ], {
       gender: Gender.FEMALE,
       teraType: PokemonType.PSYCHIC,
       instantTera: true,
-    }, {
-      species: Species.GALAR_SLOWKING,
-      gender: Gender.FEMALE,
-      teraType: PokemonType.PSYCHIC,
-      instantTera: true,
-    }]],
+    }],
     [3, { species: Species.EXEGGUTOR, gender: Gender.FEMALE }],
-    [4, [{ species: Species.WYRDEER, gender: Gender.FEMALE }, { species: Species.FARIGIRAF, gender: Gender.FEMALE }]],
+    [4, [{ species: Species.WYRDEER }, { species: Species.FARIGIRAF }], {gender: Gender.FEMALE}],
     [5, { species: Species.XATU, gender: Gender.FEMALE }]
   ],
   [TrainerType.KOGA]: [
@@ -107,11 +97,9 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     }],
     [2, [{
       species: Species.MUK,
-      instantTera: true,
-    }, {
+      }, {
       species: Species.WEEZING,
-      instantTera: true,
-    }]],
+    }], {instantTera: true}],
     [3, { species: Species.TENTACRUEL }],
     [4, [{ species: Species.SNEASLER }, { species: Species.OVERQWIL }]],
     [5, { species: Species.CROBAT }]
@@ -210,16 +198,12 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [0, { species: Species.RAPIDASH }],
     [2, [{
       species: Species.STEELIX,
-      teraType: PokemonType.FIRE,
-      instantTera: true,
       presetMoves: [Moves.FIRE_FANG],
     },
     {
       species: Species.LOPUNNY,
-      teraType: PokemonType.FIRE,
-      instantTera: true,
       presetMoves: [Moves.FIRE_PUNCH],
-    }]],
+    }], {teraType: PokemonType.FIRE, instantTera: true}],
     [3, [{ species: Species.ARCANINE }, { species: Species.HISUI_ARCANINE }]],
     [4, { species: Species.INFERNAPE }],
     [5, {
@@ -296,7 +280,7 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [0, { species: Species.KLEFKI }],
     [2, {
       species: Species.CERULEDGE,
-      instantTera: true,
+      instantTera: true, // Tera Steel Ceruledge
       presetMoves: [Moves.IRON_HEAD],
     }],
     [3, { species: Species.SCIZOR }],
@@ -307,7 +291,7 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [0, { species: Species.DRAGALGE }],
     [2, {
       species: Species.GARCHOMP,
-      instantTera: true,
+      instantTera: true, // Tera Dragon Garchomp
     }],
     [3, { species: Species.ALTARIA }],
     [4, { species: Species.DRUDDIGON }],
@@ -411,11 +395,11 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
   [TrainerType.ALLISTER_ELITE]: [
     [0, { species: Species.DUSKNOIR }],
     [2, {
-      species: Species.RUNERIGUS,
-      instantTera: true, // Tera Ghost Runerigus
+      species: Species.CURSOLA,
+      instantTera: true, // Tera Ghost Cursola
     }],
     [3, [{ species: Species.POLTEAGEIST }, { species: Species.SINISTCHA }]],
-    [4, { species: Species.CURSOLA }],
+    [4, { species: Species.RUNERIGUS }],
     [5, { species: Species.GENGAR }],
   ],
   [TrainerType.RAIHAN_ELITE]: [
@@ -441,12 +425,15 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
   [TrainerType.POPPY]: [
     [0, { species: Species.COPPERAJAH }],
     [2, { species: Species.MAGNEZONE }],
-    [3, [{
-      species: Species.CORVIKNIGHT
-    }, {
-      species: Species.BRONZONG,
-      abilityIndex: 0, // Levitate
-    }]],
+    [3, [
+      {
+        species: Species.CORVIKNIGHT
+      },
+      {
+        species: Species.BRONZONG,
+        abilityIndex: 0, // Levitate
+      }
+    ]],
     [4, { species: Species.STEELIX }],
     [5, { species: Species.TINKATON, instantTera: true }],
   ],
@@ -509,7 +496,7 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
       presetMoves: [Moves.DUAL_CHOP],
     }],
     [3, { species: Species.HAXORUS }],
-    [4, [{ species: Species.KINGDRA }, { species: Species.DRACOVISH }]],
+    [4, { species: Species.KINGDRA }],
     [5, { species: Species.ARCHALUDON }],
   ],
 
@@ -517,23 +504,15 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [0, { species: Species.ALAKAZAM }],
     [1, { species: Species.MACHAMP }],
     [2, { species: Species.HO_OH, pokeball: PokeballType.MASTER_BALL }],
-    [3, [{
-      species: Species.RHYPERIOR,
-      instantTera: true, // Tera Ground or Rock
-    }, {
-      species: Species.ELECTIVIRE,
-      instantTera: true, // Tera Electric
-    }]],
-    [4, [{
-      species: Species.ARCANINE,
-      boss: true,
-    }, {
-      species: Species.EXEGGUTOR,
-      boss: true,
-    }, {
-      species: Species.GYARADOS,
-      boss: true,
-    }]],
+    [3, [
+      {species: Species.RHYPERIOR}, // Tera Ground or Rock
+      {species: Species.ELECTIVIRE}, // Tera Electric
+    ], {instantTera: true}],
+    [4, [
+      {species: Species.ARCANINE},
+      {species: Species.EXEGGUTOR},
+      {species: Species.GYARADOS}
+    ], {boss: true}],
     [5, {
       species: Species.PIDGEOT,
       formIndex: 1, // Mega Pidgeot
@@ -547,16 +526,11 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     }],
     [1, [{ species: Species.ESPEON }, { species: Species.UMBREON }, { species: Species.SYLVEON }]],
     [2, { species: Species.LUGIA, pokeball: PokeballType.MASTER_BALL }],
-    [3, [{
-      species: Species.MEGANIUM,
-      instantTera: true, // Tera Grass
-    }, {
-      species: Species.TYPHLOSION,
-      instantTera: true, // Tera Fire
-    }, {
-      species: Species.FERALIGATR,
-      instantTera: true, // Tera Water
-    }]],
+    [3, [
+      {species: Species.MEGANIUM},
+      {species: Species.TYPHLOSION},
+      {species: Species.FERALIGATR}
+    ], {instantTera: true}],
     [4, { species: Species.SNORLAX, boss: true }],
     [5, [{
       species: Species.VENUSAUR,
@@ -578,23 +552,16 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [4, [{
       species: Species.TYRANITAR,
       abilityIndex: 2, // Unnerve
-      teraType: PokemonType.DRAGON,
-      instantTera: true,
-      presetMoves: [Moves.DRAGON_CLAW]
+      presetMoves: [Moves.DRAGON_CLAW],
     }, {
       species: Species.GARCHOMP,
       abilityIndex: 2, // Rough Skin
-      teraType: PokemonType.DRAGON,
-      instantTera: true,
     }, {
       species: Species.KOMMO_O,
       abilityIndex: 1, // Soundproof
-      teraType: PokemonType.DRAGON,
-      instantTera: true,
-    }]],
+    }], {teraType: PokemonType.DRAGON, instantTera: true}],
     [5, {
       species: Species.DRAGONITE,
-      abilityIndex: 2, // Multiscale
       boss: true,
     }]
   ],
@@ -604,19 +571,11 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [1, [{ species: Species.CRADILY }, { species: Species.ARMALDO }]],
     [2, { species: Species.AGGRON, boss: true }],
     [3, [{ species: Species.GOLURK }, { species: Species.RUNERIGUS }]],
-    [4, [{
-      species: Species.REGIROCK,
-      instantTera: true,
-      pokeball: PokeballType.ULTRA_BALL,
-    }, {
-      species: Species.REGICE,
-      instantTera: true,
-      pokeball: PokeballType.ULTRA_BALL,
-    }, {
-      species: Species.REGISTEEL,
-      instantTera: true,
-      pokeball: PokeballType.ULTRA_BALL,
-    }]],
+    [4, [
+      {species: Species.REGIROCK},
+      {species: Species.REGICE},
+      {species: Species.REGISTEEL}
+    ], {instantTera: true, pokeball: PokeballType.ULTRA_BALL}],
     [5, {
       species: Species.METAGROSS,
       formIndex: 1, // Mega Metagross
@@ -628,22 +587,15 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [2, [{
       species: Species.LATIAS,
       formIndex: 1, // Mega Latias
-      pokeball: PokeballType.MASTER_BALL,
     }, {
       species: Species.LATIOS,
       formIndex: 1, // Mega Latios
-      pokeball: PokeballType.MASTER_BALL,
-    }]],
+    }], {pokeball: PokeballType.MASTER_BALL}],
     [3, [{ species: Species.SWAMPERT }, { species: Species.GASTRODON }, { species: Species.SEISMITOAD }]],
-    [4, [{
-      species: Species.REGIELEKI,
-      instantTera: true,
-      pokeball: PokeballType.ULTRA_BALL,
-    }, {
-      species: Species.REGIDRAGO,
-      instantTera: true,
-      pokeball: PokeballType.ULTRA_BALL,
-    }]],
+    [4, [
+      {species: Species.REGIELEKI},
+      {species: Species.REGIDRAGO}
+    ], {instantTera: true, pokeball: PokeballType.ULTRA_BALL}],
     [5, {
       species: Species.MILOTIC,
       boss: true,
@@ -683,18 +635,18 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
   [TrainerType.ALDER]: [
     [0, [{ species: Species.BOUFFALANT }, { species: Species.BRAVIARY }]],
     [1, [
-      { species: Species.BASCULEGION, pokeball: PokeballType.ROGUE_BALL },
-      { species: Species.HISUI_LILLIGANT, pokeball: PokeballType.ROGUE_BALL },
-      { species: Species.HISUI_ZOROARK, pokeball: PokeballType.ROGUE_BALL },
-    ]],
+      { species: Species.BASCULEGION },
+      { species: Species.HISUI_LILLIGANT },
+      { species: Species.HISUI_ZOROARK },
+    ], {pokeball: PokeballType.ROGUE_BALL}],
     [2, { species: Species.ZEKROM, pokeball: PokeballType.MASTER_BALL }],
     [3, { species: Species.KELDEO, pokeball: PokeballType.ULTRA_BALL }],
     [4, [
-      { species: Species.CHANDELURE, teraType: PokemonType.GHOST, instantTera: true },
-      { species: Species.KROOKODILE, teraType: PokemonType.DARK, instantTera: true },
-      { species: Species.CONKELDURR, teraType: PokemonType.FIGHTING, instantTera: true },
-      { species: Species.REUNICLUS, teraType: PokemonType.PSYCHIC, instantTera: true },
-    ]],
+      { species: Species.CHANDELURE, teraType: PokemonType.GHOST },
+      { species: Species.KROOKODILE, teraType: PokemonType.DARK },
+      { species: Species.CONKELDURR, teraType: PokemonType.FIGHTING },
+      { species: Species.REUNICLUS, teraType: PokemonType.PSYCHIC },
+    ], {instantTera: true}],
     [5, { species: Species.VOLCARONA, boss: true }],
   ],
   [TrainerType.IRIS]: [
@@ -702,10 +654,10 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [1, { species: Species.ARCHEOPS }],
     [2, { species: Species.RESHIRAM, pokeball: PokeballType.MASTER_BALL }],
     [3, [
-      { species: Species.SALAMENCE, teraType: PokemonType.DRAGON, instantTera: true },
-      { species: Species.HYDREIGON, teraType: PokemonType.DRAGON, instantTera: true },
-      { species: Species.ARCHALUDON, teraType: PokemonType.DRAGON, instantTera: true },
-    ]],
+      { species: Species.SALAMENCE },
+      { species: Species.HYDREIGON },
+      { species: Species.ARCHALUDON },
+    ], {teraType: PokemonType.DRAGON, instantTera: true}],
     [4, {
       species: Species.LAPRAS,
       formIndex: 1, // G-Max Lapras
@@ -721,13 +673,11 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
       species: Species.TYRANTRUM,
       abilityIndex: 2, // Rock Head
       teraType: PokemonType.DRAGON,
-      instantTera: true,
     }, {
       species: Species.AURORUS,
       abilityIndex: 2, // Snow Warning
       teraType: PokemonType.ICE,
-      instantTera: true,
-    }]],
+    }], {instantTera: true}],
     [4, {
       species: Species.GOODRA,
       boss: true,
@@ -745,19 +695,19 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     }],
     [1, [{ species: Species.MAGNEZONE }, { species: Species.ALOLA_NINETALES }]],
     [2, [
-      { species: Species.TORNADUS, formIndex: 1, pokeball: PokeballType.ULTRA_BALL },
-      { species: Species.THUNDURUS, formIndex: 1, pokeball: PokeballType.ULTRA_BALL },
-      { species: Species.LANDORUS, formIndex: 1, pokeball: PokeballType.ULTRA_BALL },
-    ]],
+      { species: Species.TORNADUS },
+      { species: Species.THUNDURUS },
+      { species: Species.LANDORUS },
+    ], {formIndex: 1, pokeball: PokeballType.ULTRA_BALL}], // Therian Forme Genie
     [3, [
-      { species: Species.TAPU_KOKO, boss: true, pokeball: PokeballType.ULTRA_BALL },
-      { species: Species.TAPU_FINI, boss: true, pokeball: PokeballType.ULTRA_BALL },
-    ]],
+      { species: Species.TAPU_KOKO },
+      { species: Species.TAPU_FINI },
+    ], {boss: true, pokeball: PokeballType.ULTRA_BALL}],
     [4, { species: Species.SNORLAX, formIndex: 1 }], // G-Max Snorlax
     [5, [
-      { species: Species.INCINEROAR, teraType: PokemonType.DARK, instantTera: true },
-      { species: Species.HISUI_DECIDUEYE, teraType: PokemonType.FIGHTING, instantTera: true },
-    ]],
+      { species: Species.INCINEROAR, teraType: PokemonType.DARK },
+      { species: Species.HISUI_DECIDUEYE, teraType: PokemonType.FIGHTING },
+    ], {instantTera: true}],
   ],
 
   [TrainerType.HAU]: [
@@ -765,14 +715,14 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [1, { species: Species.NOIVERN }],
     [2, { species: Species.SOLGALEO, pokeball: PokeballType.MASTER_BALL }],
     [3, [
-      { species: Species.TAPU_LELE, teraType: PokemonType.PSYCHIC, instantTera: true, pokeball: PokeballType.ULTRA_BALL },
-      { species: Species.TAPU_BULU, teraType: PokemonType.GRASS, instantTera: true, pokeball: PokeballType.ULTRA_BALL },
-    ]],
+      { species: Species.TAPU_LELE, teraType: PokemonType.PSYCHIC },
+      { species: Species.TAPU_BULU, teraType: PokemonType.GRASS },
+    ], {instantTera: true, pokeball: PokeballType.ULTRA_BALL}],
     [4, { species: Species.ZYGARDE, formIndex: 1, pokeball: PokeballType.ROGUE_BALL }], // Zygarde 10% Forme, Aura Break
     [5, [
-      { species: Species.DECIDUEYE, boss: true },
-      { species: Species.PRIMARINA, boss: true, gender: Gender.FEMALE },
-    ]],
+      { species: Species.DECIDUEYE },
+      { species: Species.PRIMARINA, gender: Gender.FEMALE },
+    ], {boss: true}],
   ],
 
   [TrainerType.LEON]: [
@@ -781,10 +731,10 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [2, { species: Species.ZACIAN, pokeball: PokeballType.MASTER_BALL }],
     [3, { species: Species.DRAGAPULT, instantTera: true }], // Tera Ghost or Dragon Dragapult
     [4, [
-      { species: Species.RILLABOOM, boss: true },
-      { species: Species.CINDERACE, boss: true },
-      { species: Species.INTELEON, boss: true },
-    ]],
+      { species: Species.RILLABOOM },
+      { species: Species.CINDERACE },
+      { species: Species.INTELEON },
+    ], {boss: true}],
     [5, { species: Species.CHARIZARD, formIndex: 3 }], // G-Max Charizard
   ],
 
@@ -792,14 +742,14 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     [0, { species: Species.CORVIKNIGHT, pokeball: PokeballType.ULTRA_BALL }],
     [1, { species: Species.KOMMO_O, pokeball: PokeballType.ULTRA_BALL }],
     [2, [
-      { species: Species.GALAR_SLOWBRO, pokeball: PokeballType.ULTRA_BALL, teraType: PokemonType.POISON, instantTera: true },
-      { species: Species.GALAR_SLOWKING, pokeball: PokeballType.ULTRA_BALL, teraType: PokemonType.POISON, instantTera: true },
-    ]],
+      { species: Species.GALAR_SLOWBRO, pokeball: PokeballType.ULTRA_BALL },
+      { species: Species.GALAR_SLOWKING, pokeball: PokeballType.ULTRA_BALL },
+    ], {teraType: PokemonType.POISON, instantTera: true}],
     [3, { species: Species.GALAR_DARMANITAN, pokeball: PokeballType.ULTRA_BALL }],
     [4, [
-      { species: Species.VENUSAUR, pokeball: PokeballType.ULTRA_BALL, boss: true },
-      { species: Species.BLASTOISE, pokeball: PokeballType.ULTRA_BALL, boss: true },
-    ]],
+      { species: Species.VENUSAUR },
+      { species: Species.BLASTOISE },
+    ], {pokeball: PokeballType.ULTRA_BALL, boss: true}],
     [5, {
       species: Species.URSHIFU,
       randomForms: [2, 3], // G-Max Single Strike or G-Max Rapid Strike
@@ -837,31 +787,17 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
       {
         species: Species.ARMAROUGE,
         teraType: PokemonType.PSYCHIC,
-        instantTera: true,
       },
       {
         species: Species.CERULEDGE,
         teraType: PokemonType.GHOST,
-        instantTera: true,
       },
-    ]],
+    ], {instantTera: true}],
     [5, [
-      {
-        species: Species.MEOWSCARADA,
-        boss: true,
-        gender: Gender.MALE,
-      },
-      {
-        species: Species.SKELEDIRGE,
-        boss: true,
-        gender: Gender.MALE,
-      },
-      {
-        species: Species.QUAQUAVAL,
-        boss: true,
-        gender: Gender.MALE,
-      },
-    ]]
+      {species: Species.MEOWSCARADA},
+      {species: Species.SKELEDIRGE},
+      {species: Species.QUAQUAVAL},
+    ], {boss: true, gender: Gender.MALE}],
   ],
 
   [TrainerType.KIERAN]: [
@@ -872,9 +808,9 @@ export const trainerPartyConfigs: TrainerPartyConfigs = {
     ]],
     [2, { species: Species.TERAPAGOS, pokeball: PokeballType.MASTER_BALL }],
     [3, [
-      { species: Species.URSALUNA, pokeball: PokeballType.ULTRA_BALL },
-      { species: Species.BLOODMOON_URSALUNA, pokeball: PokeballType.ULTRA_BALL },
-    ]],
+      { species: Species.URSALUNA },
+      { species: Species.BLOODMOON_URSALUNA },
+    ], {pokeball: PokeballType.ULTRA_BALL}],
     [4, {
       species: Species.OGERPON,
       randomForms: [0, 1, 2, 3], // Choose a random Mask, which will then Tera
diff --git a/src/data/trainers/trainer-config.ts b/src/data/trainers/trainer-config.ts
index a4c7df9dc00..de908705165 100644
--- a/src/data/trainers/trainer-config.ts
+++ b/src/data/trainers/trainer-config.ts
@@ -49,14 +49,9 @@ import type {
   TrainerConfigs,
   PartyMemberFuncs,
 } from "./typedefs";
-import { PokemonPregenData } from "#app/system/pokemon-data";
+import { mergePregenData, PokemonPregenData } from "#app/system/pokemon-data";
 import { trainerPartyConfigs } from "../balance/trainers/trainer-party-configs";
 
-export type TrainerPartySetSlot = [
-  slot: number,
-  config: PokemonPregenData | PokemonPregenData[]
-]
-
 /** Minimum BST for Pokemon generated onto the Elite Four's teams */
 const ELITE_FOUR_MINIMUM_BST = 460;
 
@@ -129,6 +124,7 @@ export class TrainerConfig {
   public specialtyType: PokemonType;
   public hasVoucher = false;
   public trainerAI: TrainerAI;
+  public partyPregen: Partial<PokemonPregenData>;
 
   public encounterMessages: string[] = [];
   public victoryMessages: string[] = [];
@@ -712,22 +708,24 @@ export class TrainerConfig {
     return this;
   }
 
-  getRandomPartyMemberFuncFromConfig(cfgs: PokemonPregenData[], postProcess?: (Pokemon) => void) {
+  getRandomPartyMemberFuncFromConfig(cfgs: PokemonPregenData[], postProcess?: (Pokemon) => void, extraPregen?: Partial<PokemonPregenData>) {
     return (level: number, strength: PartyMemberStrength) => {
       let cfg: PokemonPregenData = cfgs[0];
       if (cfgs.length > 1) {
         cfg = randSeedItem(cfgs);
       }
 
-      if (cfg.teraType) { // Defined tera type: instant tera
+      if (cfg.teraType || extraPregen?.teraType) { // Defined tera type: instant tera
         cfg.instantTera = true;
       }
-      else if (cfg.instantTera && this.hasSpecialtyType()) { // Instant tera with undefined type will be specialty type
+      else if ((cfg.instantTera || extraPregen?.instantTera) && this.hasSpecialtyType()) { // Instant tera with undefined type will be specialty type
         cfg.teraType = this.specialtyType;
       }
+      const pregen = extraPregen ? mergePregenData(extraPregen, this.partyPregen) : this.partyPregen;
 
       cfg.player = false;
       cfg.level = level;
+      cfg = pregen ? mergePregenData(cfg, pregen) as PokemonPregenData : cfg;
       return globalScene.addEnemyPokemon(
         getPokemonSpecies(cfg.species),
         level,
@@ -736,7 +734,7 @@ export class TrainerConfig {
         cfg.shinyLock,
         undefined,
         postProcess,
-        cfg
+        cfg,
       );
     }
   }
@@ -762,22 +760,28 @@ export class TrainerConfig {
     // Set species filter and specialty type, otherwise filter by base total.
     this.setSpeciesFilter(p => p.isOfType(specialtyType) && p.baseTotal >= ELITE_FOUR_MINIMUM_BST);
     this.setSpecialtyType(specialtyType);
+    if (!this.partyPregen.preferredGender) {
+      this.partyPregen.preferredGender = isMale ? Gender.MALE : Gender.FEMALE;
+    }
 
     trainerPartyConfigs[this.trainerType].forEach((slot, s) => {
-      const cfg = Array.isArray(slot[1]) ? slot[1] : [slot[1]];
-      if (s === 5) { // Last party member is always a boss with 2 segments
-        cfg.forEach(c => {
-          c.boss = true;
-          c.bossSegments = 2;
-        });
+      if (!Array.isArray(slot[1])) {
+        if (s == 5) {
+          slot[1].boss = true;
+          slot[1].bossSegments = 2;
+        }
+        if (slot[1].teraType || slot[1].instantTera) {
+          this.setInstantTera(s);
+        }
+        this.setPartyMemberFunc(slot[0], this.getRandomPartyMemberFuncFromConfig([slot[1]]));
       }
-      cfg.forEach(c => {
-        c.preferredGender = c.preferredGender ?? isMale ? Gender.MALE: Gender.FEMALE;
-      });
-      if (cfg.some(c => c.teraType || c.instantTera)) {
-        this.setInstantTera(s);
+      else {
+        let pregen = slot[2] ?? undefined;
+        if (slot[2]?.teraType || slot[2]?.instantTera) {
+          this.setInstantTera(s);
+        }
+        this.setPartyMemberFunc(slot[0], this.getRandomPartyMemberFuncFromConfig(slot[1], undefined, pregen));
       }
-      this.setPartyMemberFunc(slot[0], this.getRandomPartyMemberFuncFromConfig(cfg));
     });
 
     // Localize the trainer's name by converting it to lowercase and replacing spaces with underscores.
@@ -815,22 +819,23 @@ export class TrainerConfig {
 
     // Set the party templates for the Champion.
     this.setPartyTemplates(trainerPartyTemplates.CHAMPION);
+    if (!this.partyPregen.preferredGender) {
+      this.partyPregen.preferredGender = isMale ? Gender.MALE : Gender.FEMALE;
+    }
 
     trainerPartyConfigs[this.trainerType].forEach((slot, s) => {
-      const cfg = Array.isArray(slot[1]) ? slot[1] : [slot[1]];
-      if (s === 5) { // Last party member is always a boss with 2 segments
-        cfg.forEach(c => {
-          c.boss = true;
-          c.bossSegments = 2;
-        });
+      if (!Array.isArray(slot[1])) {
+        if (slot[1].teraType || slot[1].instantTera) {
+          this.setInstantTera(s);
+        }
+        this.setPartyMemberFunc(slot[0], this.getRandomPartyMemberFuncFromConfig([slot[1]]));
       }
-      cfg.forEach(c => {
-        c.preferredGender = c.preferredGender ?? isMale ? Gender.MALE: Gender.FEMALE;
-      });
-      if (cfg.some(c => c.teraType || c.instantTera)) {
-        this.setInstantTera(s);
+      else {
+        if (slot[2]?.teraType || slot[2]?.instantTera) {
+          this.setInstantTera(s);
+        }
+        this.setPartyMemberFunc(slot[0], this.getRandomPartyMemberFuncFromConfig(slot[1], undefined, slot[2]));
       }
-      this.setPartyMemberFunc(slot[0], this.getRandomPartyMemberFuncFromConfig(cfg));
     });
 
     // Localize the trainer's name by converting it to lowercase and replacing spaces with underscores.
@@ -1044,7 +1049,7 @@ export function getRandomPartyMemberFunc(
   trainerSlot: TrainerSlot = TrainerSlot.TRAINER,
   ignoreEvolution = false,
   postProcess?: (enemyPokemon: EnemyPokemon) => void,
-  pregenData?: PokemonPregenData,
+  pregenData?: Partial<PokemonPregenData>,
 ) {
   return (level: number, strength: PartyMemberStrength) => {
     let species = randSeedItem(speciesPool);
@@ -1056,6 +1061,9 @@ export function getRandomPartyMemberFunc(
         globalScene.currentBattle.waveIndex,
       );
     }
+    if (pregenData) {
+      pregenData.species = species;
+    }
     return globalScene.addEnemyPokemon(
       getPokemonSpecies(species),
       level,
@@ -1064,7 +1072,7 @@ export function getRandomPartyMemberFunc(
       false,
       undefined,
       postProcess,
-      pregenData,
+      pregenData as PokemonPregenData ?? undefined,
     );
   };
 }
diff --git a/src/data/trainers/typedefs.ts b/src/data/trainers/typedefs.ts
index 8e916130384..6ae7bf7d0cf 100644
--- a/src/data/trainers/typedefs.ts
+++ b/src/data/trainers/typedefs.ts
@@ -1,8 +1,9 @@
 import type { EnemyPokemon } from "#app/field/pokemon";
 import type { PersistentModifier } from "#app/modifier/modifier";
+import { PokemonPregenData } from "#app/system/pokemon-data";
 import type { PartyMemberStrength } from "#enums/party-member-strength";
 import type { Species } from "#enums/species";
-import type { TrainerConfig, TrainerPartySetSlot } from "./trainer-config";
+import type { TrainerConfig } from "./trainer-config";
 import type { TrainerPartyTemplate } from "./TrainerPartyTemplate";
 
 export type PartyTemplateFunc = () => TrainerPartyTemplate;
@@ -24,3 +25,9 @@ export interface PartyMemberFuncs {
 export interface TrainerPartyConfigs {
   [key: number]: TrainerPartySetSlot[];
 }
+
+export type TrainerPartySetSlot = [
+  slot: number,
+  config: PokemonPregenData | PokemonPregenData[],
+  applyToAll?: Partial<PokemonPregenData>
+];
\ No newline at end of file
diff --git a/src/system/pokemon-data.ts b/src/system/pokemon-data.ts
index 1a101f3230a..1455ffc11de 100644
--- a/src/system/pokemon-data.ts
+++ b/src/system/pokemon-data.ts
@@ -55,6 +55,12 @@ export interface PokemonPregenData {
   fusionCustomPokemonData?: CustomPokemonData;
 }
 
+export function mergePregenData(p: Partial<PokemonPregenData>, q: Partial<PokemonPregenData>): Partial<PokemonPregenData> {
+  let ret: Partial<PokemonPregenData> = {};
+  Object.assign<typeof ret, typeof q, typeof p>(ret, q, p);
+  return ret;
+}
+
 export default class PokemonData {
   public id: number;
   public player: boolean;