diff --git a/src/data/challenge.ts b/src/data/challenge.ts
index f786152ca3d..3d67ebd0189 100644
--- a/src/data/challenge.ts
+++ b/src/data/challenge.ts
@@ -1,4 +1,5 @@
-import { BooleanHolder, type NumberHolder, randSeedItem, deepCopy } from "#app/utils/common";
+import { BooleanHolder, type NumberHolder, randSeedItem } from "#app/utils/common";
+import { deepCopy } from "#app/utils/data";
 import i18next from "i18next";
 import type { DexAttrProps, GameData } from "#app/system/game-data";
 import { defaultStarterSpecies } from "#app/system/game-data";
diff --git a/src/enums/biome.ts b/src/enums/biome.ts
index bb9eaf454cc..7284528767d 100644
--- a/src/enums/biome.ts
+++ b/src/enums/biome.ts
@@ -1,4 +1,5 @@
 export enum Biome {
+  // TODO: Should -1 be part of the enum signature (for "unknown place")
   TOWN,
   PLAINS,
   GRASS,
diff --git a/src/field/pokemon.ts b/src/field/pokemon.ts
index 6f6ce78d1b1..80c7f2fd764 100644
--- a/src/field/pokemon.ts
+++ b/src/field/pokemon.ts
@@ -819,7 +819,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
     loadPromises.push(loadMoveAnimations(this.getMoveset().map(m => m.getMove().id)));
 
     // Load the assets for the species form
-    const formIndex = !!this.summonData.illusion && useIllusion ? this.summonData.illusion.formIndex : this.formIndex;
+    const formIndex = useIllusion && this.summonData.illusion ? this.summonData.illusion.formIndex : this.formIndex;
     loadPromises.push(
       this.getSpeciesForm(false, useIllusion).loadAssets(
         this.getGender(useIllusion) === Gender.FEMALE,
@@ -836,9 +836,10 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
       );
     }
     if (this.getFusionSpeciesForm()) {
-      const fusionFormIndex = !!this.summonData.illusion && useIllusion ? this.summonData.illusion.fusionFormIndex : this.fusionFormIndex;
-      const fusionShiny = !!this.summonData.illusion && !useIllusion ? this.summonData.illusion.basePokemon!.fusionShiny : this.fusionShiny;
-      const fusionVariant = !!this.summonData.illusion && !useIllusion ? this.summonData.illusion.basePokemon!.fusionVariant : this.fusionVariant;
+      // TODO: why is fusionFormIndex using illusion if defined but fusionShiny/variant aren't?
+      const fusionFormIndex = useIllusion && this.summonData.illusion ? this.summonData.illusion.fusionFormIndex : this.fusionFormIndex;
+      const fusionShiny = !useIllusion && this.summonData.illusion?.basePokemon ? this.summonData.illusion.basePokemon.fusionShiny : this.fusionShiny;
+      const fusionVariant = !useIllusion && this.summonData.illusion?.basePokemon ? this.summonData.illusion.basePokemon.fusionVariant : this.fusionVariant;
       loadPromises.push(this.getFusionSpeciesForm(false, useIllusion).loadAssets(
         this.getFusionGender(false, useIllusion) === Gender.FEMALE,
         fusionFormIndex,
@@ -1006,7 +1007,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   }
 
   getSpriteId(ignoreOverride?: boolean): string {
-    const formIndex: integer = !!this.summonData.illusion ?  this.summonData.illusion.formIndex! : this.formIndex;
+    const formIndex = this.summonData.illusion?.formIndex ?? this.formIndex;
     return this.getSpeciesForm(ignoreOverride, true).getSpriteId(
       this.getGender(ignoreOverride, true) === Gender.FEMALE,
       formIndex,
@@ -1020,7 +1021,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
       back = this.isPlayer();
     }
 
-    const formIndex: integer = !!this.summonData.illusion ?  this.summonData.illusion.formIndex! : this.formIndex;
+    const formIndex = this.summonData.illusion?.formIndex ?? this.formIndex;
 
     return this.getSpeciesForm(ignoreOverride, true).getSpriteId(
       this.getGender(ignoreOverride, true) === Gender.FEMALE,
@@ -1045,7 +1046,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   }
 
   getFusionSpriteId(ignoreOverride?: boolean): string {
-    const fusionFormIndex: integer = !!this.summonData.illusion ?  this.summonData.illusion.fusionFormIndex! : this.fusionFormIndex;
+    const fusionFormIndex = this.summonData.illusion?.fusionFormIndex ?? this.fusionFormIndex;
     return this.getFusionSpeciesForm(ignoreOverride, true).getSpriteId(
       this.getFusionGender(ignoreOverride, true) === Gender.FEMALE,
       fusionFormIndex,
@@ -1059,7 +1060,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
       back = this.isPlayer();
     }
 
-    const fusionFormIndex: integer = !!this.summonData.illusion ?  this.summonData.illusion.fusionFormIndex! : this.fusionFormIndex;
+    const fusionFormIndex = this.summonData.illusion?.fusionFormIndex ?? this.fusionFormIndex;
 
     return this.getFusionSpeciesForm(ignoreOverride, true).getSpriteId(
       this.getFusionGender(ignoreOverride, true) === Gender.FEMALE,
@@ -1085,7 +1086,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   }
 
   getIconAtlasKey(ignoreOverride?: boolean): string {
-    const formIndex: integer = !!this.summonData.illusion ?  this.summonData.illusion.formIndex : this.formIndex;
+    const formIndex = this.summonData.illusion?.formIndex ?? this.formIndex;
     return this.getSpeciesForm(ignoreOverride, true).getIconAtlasKey(
       formIndex,
       this.shiny,
@@ -1102,7 +1103,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   }
 
   getIconId(ignoreOverride?: boolean): string {
-    const formIndex: integer = !!this.summonData.illusion ?  this.summonData.illusion.formIndex : this.formIndex;
+    const formIndex = this.summonData.illusion?.formIndex ?? this.formIndex;
     return this.getSpeciesForm(ignoreOverride, true).getIconId(
       this.getGender(ignoreOverride, true) === Gender.FEMALE,
       formIndex,
@@ -1112,7 +1113,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   }
 
   getFusionIconId(ignoreOverride?: boolean): string {
-    const fusionFormIndex: integer = !!this.summonData.illusion ?  this.summonData.illusion.fusionFormIndex! : this.fusionFormIndex;
+    const fusionFormIndex = this.summonData.illusion?.fusionFormIndex ?? this.fusionFormIndex;
     return this.getFusionSpeciesForm(ignoreOverride, true).getIconId(
       this.getFusionGender(ignoreOverride, true) === Gender.FEMALE,
       fusionFormIndex,
@@ -1128,7 +1129,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
    */
   getSpeciesForm(ignoreOverride: boolean = false, useIllusion: boolean = false): PokemonSpeciesForm {
     const species: PokemonSpecies = useIllusion && this.summonData.illusion ? getPokemonSpecies(this.summonData.illusion.species) : this.species;
-    const formIndex: integer = useIllusion && this.summonData.illusion ? this.summonData.illusion.formIndex : this.formIndex;
+    const formIndex = useIllusion && this.summonData.illusion ? this.summonData.illusion.formIndex : this.formIndex;
 
     if (!ignoreOverride && this.summonData.speciesForm) {
       return this.summonData.speciesForm;
@@ -1145,10 +1146,10 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
    * @param {boolean} useIllusion - Whether we want the fusionSpeciesForm of the illusion or not.
    */
   getFusionSpeciesForm(ignoreOverride?: boolean, useIllusion: boolean = false): PokemonSpeciesForm {
-    const fusionSpecies: PokemonSpecies = useIllusion && !!this.summonData.illusion ? this.summonData.illusion.fusionSpecies! : this.fusionSpecies!;
-    const fusionFormIndex: integer = useIllusion && !!this.summonData.illusion ? this.summonData.illusion.fusionFormIndex! : this.fusionFormIndex;
+    const fusionSpecies: PokemonSpecies = useIllusion && this.summonData.illusion ? this.summonData.illusion.fusionSpecies! : this.fusionSpecies!;
+    const fusionFormIndex = useIllusion && this.summonData.illusion ? this.summonData.illusion.fusionFormIndex! : this.fusionFormIndex;
 
-    if (!ignoreOverride && this.summonData.speciesForm) {
+    if (!ignoreOverride && this.summonData.fusionSpeciesForm) {
       return this.summonData.fusionSpeciesForm;
     }
     if (
@@ -1817,9 +1818,9 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
    * @param {boolean} useIllusion - Whether we want the fake or real gender (illusion ability).
    */
   getGender(ignoreOverride?: boolean, useIllusion: boolean = false): Gender {
-    if (useIllusion && !!this.summonData.illusion) {
-      return this.summonData.illusion.gender!;
-    } else if (!ignoreOverride && this.summonData.gender !== undefined) {
+    if (useIllusion && this.summonData.illusion) {
+      return this.summonData.illusion.gender;
+    } else if (!ignoreOverride && !isNullOrUndefined(this.summonData.gender)) {
       return this.summonData.gender;
     }
     return this.gender;
@@ -1829,9 +1830,9 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
    * @param {boolean} useIllusion - Whether we want the fake or real gender (illusion ability).
    */
   getFusionGender(ignoreOverride?: boolean, useIllusion: boolean = false): Gender {
-    if (useIllusion && !!this.summonData.illusion) {
-      return this.summonData.illusion.fusionGender!;
-    } else if (!ignoreOverride && this.summonData.fusionGender !== undefined) {
+    if (useIllusion && this.summonData.illusion?.fusionGender) {
+      return this.summonData.illusion.fusionGender;
+    } else if (!ignoreOverride && !isNullOrUndefined(this.summonData.fusionGender)) {
       return this.summonData.fusionGender;
     }
     return this.fusionGender;
@@ -1841,8 +1842,8 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
    * @param {boolean} useIllusion - Whether we want the fake or real shininess (illusion ability).
    */
   isShiny(useIllusion: boolean = false): boolean {
-    if (!useIllusion && !!this.summonData.illusion) {
-      return this.summonData.illusion.basePokemon?.shiny || (!!this.summonData.illusion.fusionSpecies && this.summonData.illusion.basePokemon?.fusionShiny) || false;
+    if (!useIllusion && this.summonData.illusion) {
+      return this.summonData.illusion.basePokemon?.shiny || (this.summonData.illusion.fusionSpecies && this.summonData.illusion.basePokemon?.fusionShiny) || false;
     } else {
       return this.shiny || (this.isFusion(useIllusion) && this.fusionShiny);
     }
@@ -1854,7 +1855,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
    * @returns `true` if the {@linkcode Pokemon} is shiny and the fusion is shiny as well, `false` otherwise
    */
   isDoubleShiny(useIllusion: boolean = false): boolean {
-    if (!useIllusion && !!this.summonData.illusion) {
+    if (!useIllusion && this.summonData.illusion?.basePokemon) {
       return this.isFusion(false) && this.summonData.illusion.basePokemon.shiny && this.summonData.illusion.basePokemon.fusionShiny;
     } else {
       return this.isFusion(useIllusion) && this.shiny && this.fusionShiny;
@@ -1865,7 +1866,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
    * @param {boolean} useIllusion - Whether we want the fake or real variant (illusion ability).
    */
   getVariant(useIllusion: boolean = false): Variant {
-    if (!useIllusion && !!this.summonData.illusion) {
+    if (!useIllusion && this.summonData.illusion) {
       return !this.isFusion(false)
       ? this.summonData.illusion.basePokemon!.variant
       : Math.max(this.variant, this.fusionVariant) as Variant;
@@ -1878,12 +1879,10 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
 
   getBaseVariant(doubleShiny: boolean): Variant {
     if (doubleShiny) {
-      return !!this.summonData.illusion
-      ? this.summonData.illusion.basePokemon!.variant
-      : this.variant;
-    } else {
-      return this.getVariant();
+      return this.summonData.illusion?.basePokemon?.variant ?? this.variant;
     }
+
+    return this.getVariant();
   }
 
   getLuck(): number {
@@ -1891,18 +1890,17 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   }
 
   isFusion(useIllusion: boolean = false): boolean {
-    if (useIllusion && !!this.summonData.illusion) {
+    if (useIllusion && this.summonData.illusion) {
       return !!this.summonData.illusion.fusionSpecies;
-    } else {
-      return !!this.fusionSpecies;
     }
+    return !!this.fusionSpecies;
   }
 
   /**
    * @param {boolean} useIllusion - Whether we want the fake name or the real name of the Pokemon (for Illusion ability).
    */
   getName(useIllusion: boolean = false): string {
-    return (!useIllusion && !!this.summonData.illusion && this.summonData.illusion.basePokemon)
+    return (!useIllusion && this.summonData.illusion?.basePokemon)
     ? this.summonData.illusion.basePokemon.name
     : this.name;
   }
@@ -7887,8 +7885,8 @@ export class PokemonSummonData {
   public moveQueue: TurnMove[] = [];
   public tags: BattlerTag[] = [];
   public abilitySuppressed = false;
-  public speciesForm: PokemonSpeciesForm | null;
-  public fusionSpeciesForm: PokemonSpeciesForm;
+  public speciesForm: PokemonSpeciesForm | null = null;
+  public fusionSpeciesForm: PokemonSpeciesForm | null = null;
   public ability: Abilities = Abilities.NONE;
   public passiveAbility: Abilities = Abilities.NONE;
   public gender: Gender;
@@ -7913,12 +7911,18 @@ export class PokemonSummonData {
   public waveTurnCount = 1;
   /** The list of moves the pokemon has used since entering the battle */
   public moveHistory: TurnMove[] = [];
+
+  constructor(source?: PokemonSummonData | Partial<PokemonSummonData>) {
+    if (!isNullOrUndefined(source)) {
+      Object.assign(this, source)
+    }
+  }
 }
 
 /**
-Persistent data for a {@linkcode Pokemon}.
-Resets at the start of a new battle (but not on switch).
-*/
+ * Persistent data for a {@linkcode Pokemon}.
+ * Resets at the start of a new battle (but not on switch).
+ */
 export class PokemonBattleData {
   /** counts the hits the pokemon received during this battle; used for {@linkcode Moves.RAGE_FIST} */
   public hitCount = 0;
@@ -7926,20 +7930,29 @@ export class PokemonBattleData {
   public hasEatenBerry: boolean = false;
   /** A list of all berries eaten in this current battle; used by {@linkcode Abilities.HARVEST} */
   public berriesEaten: BerryType[] = [];
+
+  constructor(source?: PokemonBattleData | Partial<PokemonBattleData>) {
+    if (!isNullOrUndefined(source)) {
+      this.hitCount = source.hitCount ?? 0;
+      this.hasEatenBerry = source.hasEatenBerry ?? this.hasEatenBerry;
+      this.berriesEaten = source.berriesEaten ?? this.berriesEaten;
+    }
+  }
 }
 
 /**
-Temporary data for a {@linkcode Pokemon}.
-Resets on new wave.
-*/
+ * Temporary data for a {@linkcode Pokemon}.
+ * Resets on new wave/battle start.
+ */
 export class PokemonWaveData {
   /** whether the pokemon has endured due to a {@linkcode BattlerTagType.ENDURE_TOKEN} */
   public endured = false;
   /**
-  A set of all the abilities this {@linkcode Pokemon} has used in this wave.
-  Used to track once per battle conditions, as well as (hopefully) by the updated AI.
-  */
+   * A set of all the abilities this {@linkcode Pokemon} has used in this wave.
+   * Used to track once per battle conditions, as well as (hopefully) by the updated AI for move effectiveness.
+   */
   public abilitiesApplied: Set<Abilities> = new Set<Abilities>;
+  /** Whether the pokemon's ability has been revealed or not */
   public abilityRevealed = false;
 }
 
diff --git a/src/inputs-controller.ts b/src/inputs-controller.ts
index 7fde0f2aca8..02a95f71ac4 100644
--- a/src/inputs-controller.ts
+++ b/src/inputs-controller.ts
@@ -1,5 +1,6 @@
 import Phaser from "phaser";
-import { deepCopy, getEnumValues } from "#app/utils/common";
+import { getEnumValues } from "#app/utils/common";
+import { deepCopy } from "#app/utils/data";
 import pad_generic from "./configs/inputs/pad_generic";
 import pad_unlicensedSNES from "./configs/inputs/pad_unlicensedSNES";
 import pad_xbox360 from "./configs/inputs/pad_xbox360";
diff --git a/src/phases/encounter-phase.ts b/src/phases/encounter-phase.ts
index 022d8a865b3..d50d20bea4e 100644
--- a/src/phases/encounter-phase.ts
+++ b/src/phases/encounter-phase.ts
@@ -280,6 +280,7 @@ export class EncounterPhase extends BattlePhase {
       });
 
       if (!this.loaded && battle.battleType !== BattleType.MYSTERY_ENCOUNTER) {
+        // generate modifiers for MEs, overriding prior ones as applicable
         regenerateModifierPoolThresholds(
           globalScene.getEnemyField(),
           battle.battleType === BattleType.TRAINER ? ModifierPoolType.TRAINER : ModifierPoolType.WILD,
@@ -292,8 +293,8 @@ export class EncounterPhase extends BattlePhase {
         }
       }
 
-      if (battle.battleType === BattleType.TRAINER) {
-        globalScene.currentBattle.trainer!.genAI(globalScene.getEnemyParty());
+      if (battle.battleType === BattleType.TRAINER && globalScene.currentBattle.trainer) {
+        globalScene.currentBattle.trainer.genAI(globalScene.getEnemyParty());
       }
 
       globalScene.ui.setMode(UiMode.MESSAGE).then(() => {
@@ -336,7 +337,7 @@ export class EncounterPhase extends BattlePhase {
     for (const pokemon of globalScene.getPlayerParty()) {
       // Only reset wave data, not battle data
       if (pokemon) {
-        pokemon.resetWaveData();
+        pokemon.resetBattleAndWaveData();
       }
     }
 
diff --git a/src/system/pokemon-data.ts b/src/system/pokemon-data.ts
index e3af7b0edfe..e32ce707b98 100644
--- a/src/system/pokemon-data.ts
+++ b/src/system/pokemon-data.ts
@@ -4,17 +4,12 @@ import type { Gender } from "../data/gender";
 import { Nature } from "#enums/nature";
 import type { PokeballType } from "#enums/pokeball";
 import { getPokemonSpecies, getPokemonSpeciesForm } from "../data/pokemon-species";
-import { Status } from "../data/status-effect";
-import Pokemon, {
-  EnemyPokemon,
-  type PokemonMove,
-  type PokemonSummonData,
-  type PokemonBattleData,
-} from "../field/pokemon";
+import type { Status } from "../data/status-effect";
+import Pokemon, { EnemyPokemon, PokemonBattleData, PokemonMove, PokemonSummonData } from "../field/pokemon";
 import { TrainerSlot } from "#enums/trainer-slot";
 import type { Variant } from "#app/sprites/variant";
 import type { Biome } from "#enums/biome";
-import type { Moves } from "#enums/moves";
+import { Moves } from "#enums/moves";
 import type { Species } from "#enums/species";
 import { CustomPokemonData } from "#app/data/custom-pokemon-data";
 import type { PokemonType } from "#enums/pokemon-type";
@@ -67,8 +62,8 @@ export default class PokemonData {
   public bossSegments?: number;
 
   // Effects that need to be preserved between waves
-  public summonData: PokemonSummonData;
-  public battleData: PokemonBattleData;
+  public summonData: PokemonSummonData = new PokemonSummonData();
+  public battleData: PokemonBattleData = new PokemonBattleData();
   public summonDataSpeciesFormIndex: number;
 
   public customPokemonData: CustomPokemonData;
@@ -79,14 +74,14 @@ export default class PokemonData {
    * or JSON representation thereof.
    * @param source The {@linkcode Pokemon} to convert into data (or a JSON object representing one)
    */
-  // TODO: Remove any from type signature
+  // TODO: Remove any from type signature in favor of 2 separate method funcs
   constructor(source: Pokemon | any) {
     const sourcePokemon = source instanceof Pokemon ? source : undefined;
+
     this.id = source.id;
-    this.player = sourcePokemon ? sourcePokemon.isPlayer() : source.player;
-    this.species = sourcePokemon ? sourcePokemon.species.speciesId : source.species;
-    this.nickname =
-      sourcePokemon?.summonData.illusion?.basePokemon.nickname ?? sourcePokemon?.nickname ?? source.nickname;
+    this.player = sourcePokemon?.isPlayer() ?? source.player;
+    this.species = sourcePokemon?.species.speciesId ?? source.species;
+    this.nickname = sourcePokemon?.summonData.illusion?.basePokemon.nickname ?? source.nickname;
     this.formIndex = Math.max(Math.min(source.formIndex, getPokemonSpecies(this.species).forms.length - 1), 0);
     this.abilityIndex = source.abilityIndex;
     this.passive = source.passive;
@@ -95,60 +90,49 @@ export default class PokemonData {
     this.pokeball = source.pokeball;
     this.level = source.level;
     this.exp = source.exp;
+    this.levelExp = source.levelExp;
     this.gender = source.gender;
+    this.hp = source.hp;
     this.stats = source.stats;
     this.ivs = source.ivs;
+
+    // TODO: Can't we move some of this verification stuff to an upgrade script?
     this.nature = source.nature ?? Nature.HARDY;
+    this.moveset = source.moveset ?? [new PokemonMove(Moves.TACKLE), new PokemonMove(Moves.GROWL)];
+    this.status = source.status ?? null;
     this.friendship = source.friendship ?? getPokemonSpecies(this.species).baseFriendship;
     this.metLevel = source.metLevel || 5;
     this.metBiome = source.metBiome ?? -1;
     this.metSpecies = source.metSpecies;
     this.metWave = source.metWave ?? (this.metBiome === -1 ? -1 : 0);
     this.luck = source.luck ?? (source.shiny ? source.variant + 1 : 0);
+    this.pauseEvolutions = !!source.pauseEvolutions;
     this.pokerus = !!source.pokerus;
+    this.usedTMs = source.usedTMs ?? [];
+    this.evoCounter = source.evoCounter ?? 0;
     this.teraType = source.teraType as PokemonType;
     this.isTerastallized = !!source.isTerastallized;
     this.stellarTypesBoosted = source.stellarTypesBoosted ?? [];
 
-    this.fusionSpecies = sourcePokemon ? sourcePokemon.fusionSpecies?.speciesId : source.fusionSpecies;
+    this.fusionSpecies = sourcePokemon?.fusionSpecies?.speciesId ?? source.fusionSpecies;
     this.fusionFormIndex = source.fusionFormIndex;
     this.fusionAbilityIndex = source.fusionAbilityIndex;
-    this.fusionShiny =
-      sourcePokemon?.summonData.illusion?.basePokemon.fusionShiny ?? sourcePokemon?.fusionShiny ?? source.fusionShiny;
-    this.fusionVariant =
-      sourcePokemon?.summonData.illusion?.basePokemon.fusionVariant ??
-      sourcePokemon?.fusionVariant ??
-      source.fusionVariant;
+    this.fusionShiny = sourcePokemon?.summonData.illusion?.basePokemon.fusionShiny ?? source.fusionShiny;
+    this.fusionVariant = sourcePokemon?.summonData.illusion?.basePokemon.fusionVariant ?? source.fusionVariant;
     this.fusionGender = source.fusionGender;
     this.fusionLuck = source.fusionLuck ?? (source.fusionShiny ? source.fusionVariant + 1 : 0);
-    this.fusionCustomPokemonData = new CustomPokemonData(source.fusionCustomPokemonData);
     this.fusionTeraType = (source.fusionTeraType ?? 0) as PokemonType;
-    this.usedTMs = source.usedTMs ?? [];
-
-    this.customPokemonData = new CustomPokemonData(source.customPokemonData);
-
-    this.moveset = sourcePokemon?.moveset ?? source.moveset;
-
-    this.levelExp = source.levelExp;
-    this.hp = source.hp;
-
-    this.pauseEvolutions = !!source.pauseEvolutions;
-    this.evoCounter = source.evoCounter ?? 0;
 
     this.boss = (source instanceof EnemyPokemon && !!source.bossSegments) || (!this.player && !!source.boss);
     this.bossSegments = source.bossSegments ?? 0;
-    this.status =
-      sourcePokemon?.status ??
-      (source.status
-        ? new Status(source.status.effect, source.status.toxicTurnCount, source.status.sleepTurnsRemaining)
-        : null);
 
-    this.summonData = source.summonData;
-    this.battleData = source.battleData;
+    this.summonData = new PokemonSummonData(source.summonData);
+    this.battleData = new PokemonBattleData(source.battleData);
+    this.summonDataSpeciesFormIndex =
+      sourcePokemon?.summonData.speciesForm?.formIndex ?? source.summonDataSpeciesFormIndex;
 
-    this.summonDataSpeciesFormIndex = sourcePokemon
-      ? this.getSummonDataSpeciesFormIndex()
-      : source.summonDataSpeciesFormIndex;
+    this.customPokemonData = new CustomPokemonData(source.customPokemonData);
+    this.fusionCustomPokemonData = new CustomPokemonData(source.fusionCustomPokemonData);
   }
 
   toPokemon(battleType?: BattleType, partyMemberIndex = 0, double = false): Pokemon {
@@ -197,16 +181,4 @@ export default class PokemonData {
     }
     return ret;
   }
-
-  /**
-   * Method to save summon data species form index
-   * Necessary in case the pokemon is transformed
-   * to reload the correct form
-   */
-  getSummonDataSpeciesFormIndex(): number {
-    if (this.summonData.speciesForm) {
-      return this.summonData.speciesForm.formIndex;
-    }
-    return 0;
-  }
 }
diff --git a/src/system/version_migration/versions/v1_9_0.ts b/src/system/version_migration/versions/v1_9_0.ts
index 06e0e6de221..f0301aec230 100644
--- a/src/system/version_migration/versions/v1_9_0.ts
+++ b/src/system/version_migration/versions/v1_9_0.ts
@@ -1,5 +1,6 @@
 import type { SessionSaveMigrator } from "#app/@types/SessionSaveMigrator";
 import { loadBattlerTag } from "#app/data/battler-tags";
+import { Status } from "#app/data/status-effect";
 import { PokemonMove } from "#app/field/pokemon";
 import type { SessionSaveData } from "#app/system/game-data";
 import PokemonData from "#app/system/pokemon-data";
@@ -14,8 +15,14 @@ import { PokeballType } from "#enums/pokeball";
 const migratePartyData: SessionSaveMigrator = {
   version: "1.9.0",
   migrate: (data: SessionSaveData): void => {
+    // this stuff is copied straight from the constructor fwiw
     const mapParty = (pkmnData: PokemonData) => {
-      // this stuff is copied straight from the constructor fwiw
+      pkmnData.status &&= new Status(
+        pkmnData.status.effect,
+        pkmnData.status.toxicTurnCount,
+        pkmnData.status.sleepTurnsRemaining,
+      );
+      // remove empty moves from moveset
       pkmnData.moveset = pkmnData.moveset.filter(m => !!m) ?? [
         new PokemonMove(Moves.TACKLE),
         new PokemonMove(Moves.GROWL),
diff --git a/src/utils/common.ts b/src/utils/common.ts
index 1501e206d2d..847f8a7ecdb 100644
--- a/src/utils/common.ts
+++ b/src/utils/common.ts
@@ -467,16 +467,6 @@ export function truncateString(str: string, maxLength = 10) {
   return str;
 }
 
-/**
- * Perform a deep copy of an object.
- * @param values - The object to be deep copied.
- * @returns A new object that is a deep copy of the input.
- */
-export function deepCopy(values: object): object {
-  // Convert the object to a JSON string and parse it back to an object to perform a deep copy
-  return JSON.parse(JSON.stringify(values));
-}
-
 /**
  * Convert a space-separated string into a capitalized and underscored string.
  * @param input - The string to be converted.
diff --git a/src/utils/data.ts b/src/utils/data.ts
index 026d8c475a7..abf5327b7cb 100644
--- a/src/utils/data.ts
+++ b/src/utils/data.ts
@@ -1,3 +1,13 @@
+/**
+ * Perform a deep copy of an object.
+ * @param values - The object to be deep copied.
+ * @returns A new object that is a deep copy of the input.
+ */
+export function deepCopy(values: object): object {
+  // Convert the object to a JSON string and parse it back to an object to perform a deep copy
+  return JSON.parse(JSON.stringify(values));
+}
+
 /**
  * Deeply merge two JSON objects' common properties together.
  * This copies all values from `source` that match properties inside `dest`,
@@ -18,16 +28,17 @@ export function deepMergeSpriteData(dest: object, source: object) {
     const sourceVal = source[key];
 
     return (
-      // Somewhat redundant, but makes it clear that we're explicitly interested in properties that exist in both
+      // 1st part somewhat redundant, but makes it clear that we're explicitly interested in properties that exist in both
       key in source && Array.isArray(sourceVal) === Array.isArray(destVal) && typeof sourceVal === typeof destVal
     );
   });
 
   for (const key of matchingKeys) {
-    if (typeof source[key] === "object" && source[key] !== null && !Array.isArray(source[key])) {
-      deepMergeSpriteData(dest[key], source[key]);
-    } else {
+    // Pure objects get recursed into; everything else gets overwritten
+    if (typeof source[key] !== "object" || source[key] === null || Array.isArray(source[key])) {
       dest[key] = source[key];
+    } else {
+      deepMergeSpriteData(dest[key], source[key]);
     }
   }
 }
diff --git a/test/moves/rage_fist.test.ts b/test/moves/rage_fist.test.ts
index 60ddf4b5deb..57bc5ef563b 100644
--- a/test/moves/rage_fist.test.ts
+++ b/test/moves/rage_fist.test.ts
@@ -7,6 +7,7 @@ import type Move from "#app/data/moves/move";
 import GameManager from "#test/testUtils/gameManager";
 import Phaser from "phaser";
 import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
+import { BattleType } from "#enums/battle-type";
 
 describe("Moves - Rage Fist", () => {
   let phaserGame: Phaser.Game;
@@ -126,18 +127,31 @@ describe("Moves - Rage Fist", () => {
     expect(game.scene.getPlayerPokemon()?.battleData.hitCount).toBe(4);
   });
 
-  it("should reset hits recieved during trainer battles", async () => {
-    game.override.enemySpecies(Species.MAGIKARP).startingWave(19);
+  it("should reset hits recieved before trainer battles", async () => {
+    game.override.enemySpecies(Species.MAGIKARP).moveset(Moves.DOUBLE_IRON_BASH);
+    await game.classicMode.startBattle([Species.MARSHADOW]);
 
-    await game.classicMode.startBattle([Species.MAGIKARP]);
+    const marshadow = game.scene.getPlayerPokemon()!;
+    expect(marshadow).toBeDefined();
 
+    // beat up a magikarp
     game.move.select(Moves.RAGE_FIST);
     await game.setTurnOrder([BattlerIndex.ENEMY, BattlerIndex.PLAYER]);
+    await game.phaseInterceptor.to("TurnEndPhase");
+
+    expect(game.isVictory()).toBe(true);
+    expect(marshadow.battleData.hitCount).toBe(2);
+    expect(move.calculateBattlePower).toHaveLastReturnedWith(150);
+
+    game.override.battleType(BattleType.TRAINER);
     await game.toNextWave();
 
+    expect(game.scene.lastEnemyTrainer).not.toBeNull();
+    expect(marshadow.battleData.hitCount).toBe(0);
+
     game.move.select(Moves.RAGE_FIST);
     await game.setTurnOrder([BattlerIndex.ENEMY, BattlerIndex.PLAYER]);
-    await game.phaseInterceptor.to("BerryPhase", false);
+    await game.phaseInterceptor.to("TurnEndPhase");
 
     expect(move.calculateBattlePower).toHaveLastReturnedWith(150);
   });
diff --git a/test/settingMenu/rebinding_setting.test.ts b/test/settingMenu/rebinding_setting.test.ts
index 45c647248c4..20a1fe51484 100644
--- a/test/settingMenu/rebinding_setting.test.ts
+++ b/test/settingMenu/rebinding_setting.test.ts
@@ -2,7 +2,7 @@ import cfg_keyboard_qwerty from "#app/configs/inputs/cfg_keyboard_qwerty";
 import { getKeyWithKeycode, getKeyWithSettingName } from "#app/configs/inputs/configHandler";
 import type { InterfaceConfig } from "#app/inputs-controller";
 import { SettingKeyboard } from "#app/system/settings/settings-keyboard";
-import { deepCopy } from "#app/utils/common";
+import { deepCopy } from "#app/utils/data";
 import { Button } from "#enums/buttons";
 import { Device } from "#enums/devices";
 import { InGameManip } from "#test/settingMenu/helpers/inGameManip";