diff --git a/src/battle-scene.ts b/src/battle-scene.ts
index b802466ee19..9491753f6a3 100644
--- a/src/battle-scene.ts
+++ b/src/battle-scene.ts
@@ -894,9 +894,19 @@ export default class BattleScene extends SceneBase {
     return activeOnly ? this.infoToggles.filter(t => t?.isActive()) : this.infoToggles;
   }
 
-  getPokemonById(pokemonId: number): Pokemon | null {
-    const findInParty = (party: Pokemon[]) => party.find(p => p.id === pokemonId);
-    return (findInParty(this.getPlayerParty()) || findInParty(this.getEnemyParty())) ?? null;
+  /**
+   * Return the {@linkcode Pokemon} associated with a given ID.
+   * @param pokemonId - The ID whose Pokemon will be retrieved.
+   * @returns The {@linkcode Pokemon} associated with the given id.
+   * Returns `null` if the ID is `undefined` or not present in either party.
+   */
+  getPokemonById(pokemonId: number | undefined): Pokemon | null {
+    if (isNullOrUndefined(pokemonId)) {
+      return null;
+    }
+
+    const party = (this.getPlayerParty() as Pokemon[]).concat(this.getEnemyParty());
+    return party.find(p => p.id === pokemonId) ?? null;
   }
 
   addPlayerPokemon(
diff --git a/src/data/arena-tag.ts b/src/data/arena-tag.ts
index 494a0438b18..a1bb493bd5b 100644
--- a/src/data/arena-tag.ts
+++ b/src/data/arena-tag.ts
@@ -72,10 +72,11 @@ export abstract class ArenaTag {
 
   /**
    * Helper function that retrieves the source Pokemon
-   * @returns The source {@linkcode Pokemon} or `null` if none is found
+   * @returns - The source {@linkcode Pokemon} for this tag.
+   * Returns `null` if `this.sourceId` is `undefined`
    */
   public getSourcePokemon(): Pokemon | null {
-    return this.sourceId ? globalScene.getPokemonById(this.sourceId) : null;
+    return globalScene.getPokemonById(this.sourceId);
   }
 
   /**
@@ -107,19 +108,22 @@ export class MistTag extends ArenaTag {
   onAdd(arena: Arena, quiet = false): void {
     super.onAdd(arena);
 
-    if (this.sourceId) {
-      const source = globalScene.getPokemonById(this.sourceId);
-
-      if (!quiet && source) {
-        globalScene.phaseManager.queueMessage(
-          i18next.t("arenaTag:mistOnAdd", {
-            pokemonNameWithAffix: getPokemonNameWithAffix(source),
-          }),
-        );
-      } else if (!quiet) {
-        console.warn("Failed to get source for MistTag onAdd");
-      }
+    // We assume `quiet=true` means "just add the bloody tag no questions asked"
+    if (quiet) {
+      return;
     }
+
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for MistTag on add message; id: ${this.sourceId}`);
+      return;
+    }
+
+    globalScene.phaseManager.queueMessage(
+      i18next.t("arenaTag:mistOnAdd", {
+        pokemonNameWithAffix: getPokemonNameWithAffix(source),
+      }),
+    );
   }
 
   /**
@@ -440,18 +444,18 @@ class MatBlockTag extends ConditionalProtectTag {
   }
 
   onAdd(_arena: Arena) {
-    if (this.sourceId) {
-      const source = globalScene.getPokemonById(this.sourceId);
-      if (source) {
-        globalScene.phaseManager.queueMessage(
-          i18next.t("arenaTag:matBlockOnAdd", {
-            pokemonNameWithAffix: getPokemonNameWithAffix(source),
-          }),
-        );
-      } else {
-        console.warn("Failed to get source for MatBlockTag onAdd");
-      }
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for Mat Block message; id: ${this.sourceId}`);
+      return;
     }
+
+    super.onAdd(_arena);
+    globalScene.phaseManager.queueMessage(
+      i18next.t("arenaTag:matBlockOnAdd", {
+        pokemonNameWithAffix: getPokemonNameWithAffix(source),
+      }),
+    );
   }
 }
 
@@ -511,7 +515,12 @@ export class NoCritTag extends ArenaTag {
 
   /** Queues a message upon removing this effect from the field */
   onRemove(_arena: Arena): void {
-    const source = globalScene.getPokemonById(this.sourceId!); // TODO: is this bang correct?
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for NoCritTag on remove message; id: ${this.sourceId}`);
+      return;
+    }
+
     globalScene.phaseManager.queueMessage(
       i18next.t("arenaTag:noCritOnRemove", {
         pokemonNameWithAffix: getPokemonNameWithAffix(source ?? undefined),
@@ -522,7 +531,7 @@ export class NoCritTag extends ArenaTag {
 }
 
 /**
- * Arena Tag class for {@link https://bulbapedia.bulbagarden.net/wiki/Wish_(move) Wish}.
+ * Arena Tag class for {@link https://bulbapedia.bulbagarden.net/wiki/Wish_(move) | Wish}.
  * Heals the Pokémon in the user's position the turn after Wish is used.
  */
 class WishTag extends ArenaTag {
@@ -535,18 +544,20 @@ class WishTag extends ArenaTag {
   }
 
   onAdd(_arena: Arena): void {
-    if (this.sourceId) {
-      const user = globalScene.getPokemonById(this.sourceId);
-      if (user) {
-        this.battlerIndex = user.getBattlerIndex();
-        this.triggerMessage = i18next.t("arenaTag:wishTagOnAdd", {
-          pokemonNameWithAffix: getPokemonNameWithAffix(user),
-        });
-        this.healHp = toDmgValue(user.getMaxHp() / 2);
-      } else {
-        console.warn("Failed to get source for WishTag onAdd");
-      }
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for WishTag on add message; id: ${this.sourceId}`);
+      return;
     }
+
+    super.onAdd(_arena);
+    this.healHp = toDmgValue(source.getMaxHp() / 2);
+
+    globalScene.phaseManager.queueMessage(
+      i18next.t("arenaTag:wishTagOnAdd", {
+        pokemonNameWithAffix: getPokemonNameWithAffix(source),
+      }),
+    );
   }
 
   onRemove(_arena: Arena): void {
@@ -741,15 +752,23 @@ class SpikesTag extends ArenaTrapTag {
   onAdd(arena: Arena, quiet = false): void {
     super.onAdd(arena);
 
-    const source = this.sourceId ? globalScene.getPokemonById(this.sourceId) : null;
-    if (!quiet && source) {
-      globalScene.phaseManager.queueMessage(
-        i18next.t("arenaTag:spikesOnAdd", {
-          moveName: this.getMoveName(),
-          opponentDesc: source.getOpponentDescriptor(),
-        }),
-      );
+    // We assume `quiet=true` means "just add the bloody tag no questions asked"
+    if (quiet) {
+      return;
     }
+
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for SpikesTag on add message; id: ${this.sourceId}`);
+      return;
+    }
+
+    globalScene.phaseManager.queueMessage(
+      i18next.t("arenaTag:spikesOnAdd", {
+        moveName: this.getMoveName(),
+        opponentDesc: source.getOpponentDescriptor(),
+      }),
+    );
   }
 
   override activateTrap(pokemon: Pokemon, simulated: boolean): boolean {
@@ -794,15 +813,23 @@ class ToxicSpikesTag extends ArenaTrapTag {
   onAdd(arena: Arena, quiet = false): void {
     super.onAdd(arena);
 
-    const source = this.sourceId ? globalScene.getPokemonById(this.sourceId) : null;
-    if (!quiet && source) {
-      globalScene.phaseManager.queueMessage(
-        i18next.t("arenaTag:toxicSpikesOnAdd", {
-          moveName: this.getMoveName(),
-          opponentDesc: source.getOpponentDescriptor(),
-        }),
-      );
+    if (quiet) {
+      // We assume `quiet=true` means "just add the bloody tag no questions asked"
+      return;
     }
+
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for ToxicSpikesTag on add message; id: ${this.sourceId}`);
+      return;
+    }
+
+    globalScene.phaseManager.queueMessage(
+      i18next.t("arenaTag:toxicSpikesOnAdd", {
+        moveName: this.getMoveName(),
+        opponentDesc: source.getOpponentDescriptor(),
+      }),
+    );
   }
 
   onRemove(arena: Arena): void {
@@ -905,7 +932,11 @@ class StealthRockTag extends ArenaTrapTag {
   onAdd(arena: Arena, quiet = false): void {
     super.onAdd(arena);
 
-    const source = this.sourceId ? globalScene.getPokemonById(this.sourceId) : null;
+    if (quiet) {
+      return;
+    }
+
+    const source = this.getSourcePokemon();
     if (!quiet && source) {
       globalScene.phaseManager.queueMessage(
         i18next.t("arenaTag:stealthRockOnAdd", {
@@ -989,15 +1020,24 @@ class StickyWebTag extends ArenaTrapTag {
 
   onAdd(arena: Arena, quiet = false): void {
     super.onAdd(arena);
-    const source = this.sourceId ? globalScene.getPokemonById(this.sourceId) : null;
-    if (!quiet && source) {
-      globalScene.phaseManager.queueMessage(
-        i18next.t("arenaTag:stickyWebOnAdd", {
-          moveName: this.getMoveName(),
-          opponentDesc: source.getOpponentDescriptor(),
-        }),
-      );
+
+    // We assume `quiet=true` means "just add the bloody tag no questions asked"
+    if (quiet) {
+      return;
     }
+
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for SpikesTag on add message; id: ${this.sourceId}`);
+      return;
+    }
+
+    globalScene.phaseManager.queueMessage(
+      i18next.t("arenaTag:stickyWebOnAdd", {
+        moveName: this.getMoveName(),
+        opponentDesc: source.getOpponentDescriptor(),
+      }),
+    );
   }
 
   override activateTrap(pokemon: Pokemon, simulated: boolean): boolean {
@@ -1061,14 +1101,20 @@ export class TrickRoomTag extends ArenaTag {
   }
 
   onAdd(_arena: Arena): void {
-    const source = this.sourceId ? globalScene.getPokemonById(this.sourceId) : null;
-    if (source) {
-      globalScene.phaseManager.queueMessage(
-        i18next.t("arenaTag:trickRoomOnAdd", {
-          pokemonNameWithAffix: getPokemonNameWithAffix(source),
-        }),
-      );
+    super.onAdd(_arena);
+
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for TrickRoomTag on add message; id: ${this.sourceId}`);
+      return;
     }
+
+    globalScene.phaseManager.queueMessage(
+      i18next.t("arenaTag:trickRoomOnAdd", {
+        moveName: this.getMoveName(),
+        opponentDesc: source.getOpponentDescriptor(),
+      }),
+    );
   }
 
   onRemove(_arena: Arena): void {
@@ -1115,6 +1161,13 @@ class TailwindTag extends ArenaTag {
   }
 
   onAdd(_arena: Arena, quiet = false): void {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      return;
+    }
+
+    super.onAdd(_arena, quiet);
+
     if (!quiet) {
       globalScene.phaseManager.queueMessage(
         i18next.t(
@@ -1123,15 +1176,14 @@ class TailwindTag extends ArenaTag {
       );
     }
 
-    const source = globalScene.getPokemonById(this.sourceId!); //TODO: this bang is questionable!
-    const party = (source?.isPlayer() ? globalScene.getPlayerField() : globalScene.getEnemyField()) ?? [];
-    const phaseManager = globalScene.phaseManager;
+    const field = source.isPlayer() ? globalScene.getPlayerField() : globalScene.getEnemyField();
 
-    for (const pokemon of party) {
+    for (const pokemon of field) {
       // Apply the CHARGED tag to party members with the WIND_POWER ability
+      // TODO: This should not be handled here
       if (pokemon.hasAbility(AbilityId.WIND_POWER) && !pokemon.getTag(BattlerTagType.CHARGED)) {
         pokemon.addTag(BattlerTagType.CHARGED);
-        phaseManager.queueMessage(
+        globalScene.phaseManager.queueMessage(
           i18next.t("abilityTriggers:windPowerCharged", {
             pokemonName: getPokemonNameWithAffix(pokemon),
             moveName: this.getMoveName(),
@@ -1142,9 +1194,16 @@ class TailwindTag extends ArenaTag {
       // Raise attack by one stage if party member has WIND_RIDER ability
       // TODO: Ability displays should be handled by the ability
       if (pokemon.hasAbility(AbilityId.WIND_RIDER)) {
-        phaseManager.queueAbilityDisplay(pokemon, false, true);
-        phaseManager.unshiftNew("StatStageChangePhase", pokemon.getBattlerIndex(), true, [Stat.ATK], 1, true);
-        phaseManager.queueAbilityDisplay(pokemon, false, false);
+        globalScene.phaseManager.queueAbilityDisplay(pokemon, false, true);
+        globalScene.phaseManager.unshiftNew(
+          "StatStageChangePhase",
+          pokemon.getBattlerIndex(),
+          true,
+          [Stat.ATK],
+          1,
+          true,
+        );
+        globalScene.phaseManager.queueAbilityDisplay(pokemon, false, false);
       }
     }
   }
@@ -1216,24 +1275,26 @@ class ImprisonTag extends ArenaTrapTag {
   }
 
   /**
-   * This function applies the effects of Imprison to the opposing Pokemon already present on the field.
-   * @param arena
+   * Apply the effects of Imprison to all opposing on-field Pokemon.
    */
   override onAdd() {
     const source = this.getSourcePokemon();
-    if (source) {
-      const party = this.getAffectedPokemon();
-      party?.forEach((p: Pokemon) => {
-        if (p.isAllowedInBattle()) {
-          p.addTag(BattlerTagType.IMPRISON, 1, MoveId.IMPRISON, this.sourceId);
-        }
-      });
-      globalScene.phaseManager.queueMessage(
-        i18next.t("battlerTags:imprisonOnAdd", {
-          pokemonNameWithAffix: getPokemonNameWithAffix(source),
-        }),
-      );
+    if (!source) {
+      return;
     }
+
+    const party = this.getAffectedPokemon();
+    party.forEach(p => {
+      if (p.isAllowedInBattle()) {
+        p.addTag(BattlerTagType.IMPRISON, 1, MoveId.IMPRISON, this.sourceId);
+      }
+    });
+
+    globalScene.phaseManager.queueMessage(
+      i18next.t("battlerTags:imprisonOnAdd", {
+        pokemonNameWithAffix: getPokemonNameWithAffix(source),
+      }),
+    );
   }
 
   /**
@@ -1243,7 +1304,7 @@ class ImprisonTag extends ArenaTrapTag {
    */
   override lapse(): boolean {
     const source = this.getSourcePokemon();
-    return source ? source.isActive(true) : false;
+    return !!source?.isActive(true);
   }
 
   /**
@@ -1265,9 +1326,7 @@ class ImprisonTag extends ArenaTrapTag {
    */
   override onRemove(): void {
     const party = this.getAffectedPokemon();
-    party?.forEach((p: Pokemon) => {
-      p.removeTag(BattlerTagType.IMPRISON);
-    });
+    party.forEach(p => p.removeTag(BattlerTagType.IMPRISON));
   }
 }
 
diff --git a/src/data/battler-tags.ts b/src/data/battler-tags.ts
index 8405fd1dd4d..cfc5c1b4ea9 100644
--- a/src/data/battler-tags.ts
+++ b/src/data/battler-tags.ts
@@ -111,7 +111,7 @@ export class BattlerTag {
    * @returns The source {@linkcode Pokemon}, or `null` if none is found
    */
   public getSourcePokemon(): Pokemon | null {
-    return this.sourceId ? globalScene.getPokemonById(this.sourceId) : null;
+    return globalScene.getPokemonById(this.sourceId);
   }
 }
 
@@ -540,9 +540,13 @@ export class TrappedTag extends BattlerTag {
   }
 
   canAdd(pokemon: Pokemon): boolean {
-    const source = globalScene.getPokemonById(this.sourceId!)!;
-    const move = allMoves[this.sourceMove];
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for TrappedTag canAdd; id: ${this.sourceId}`);
+      return false;
+    }
 
+    const move = allMoves[this.sourceMove];
     const isGhost = pokemon.isOfType(PokemonType.GHOST);
     const isTrapped = pokemon.getTag(TrappedTag);
     const hasSubstitute = move.hitsSubstitute(source, pokemon);
@@ -763,12 +767,20 @@ export class DestinyBondTag extends BattlerTag {
     if (lapseType !== BattlerTagLapseType.CUSTOM) {
       return super.lapse(pokemon, lapseType);
     }
-    const source = this.sourceId ? globalScene.getPokemonById(this.sourceId) : null;
-    if (!source?.isFainted()) {
+
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for DestinyBondTag lapse; id: ${this.sourceId}`);
+      return false;
+    }
+
+    // Destiny bond stays active until the user faints
+    if (!source.isFainted()) {
       return true;
     }
 
-    if (source?.getAlly() === pokemon) {
+    // Don't kill allies or opposing bosses.
+    if (source.getAlly() === pokemon) {
       return false;
     }
 
@@ -781,6 +793,7 @@ export class DestinyBondTag extends BattlerTag {
       return false;
     }
 
+    // Drag the foe down with the user
     globalScene.phaseManager.queueMessage(
       i18next.t("battlerTags:destinyBondLapse", {
         pokemonNameWithAffix: getPokemonNameWithAffix(source),
@@ -798,17 +811,13 @@ export class InfatuatedTag extends BattlerTag {
   }
 
   canAdd(pokemon: Pokemon): boolean {
-    if (this.sourceId) {
-      const pkm = globalScene.getPokemonById(this.sourceId);
-
-      if (pkm) {
-        return pokemon.isOppositeGender(pkm);
-      }
-      console.warn("canAdd: this.sourceId is not a valid pokemon id!", this.sourceId);
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for InfatuatedTag canAdd; id: ${this.sourceId}`);
       return false;
     }
-    console.warn("canAdd: this.sourceId is undefined");
-    return false;
+
+    return pokemon.isOppositeGender(source);
   }
 
   onAdd(pokemon: Pokemon): void {
@@ -817,7 +826,7 @@ export class InfatuatedTag extends BattlerTag {
     globalScene.phaseManager.queueMessage(
       i18next.t("battlerTags:infatuatedOnAdd", {
         pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-        sourcePokemonName: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
+        sourcePokemonName: getPokemonNameWithAffix(this.getSourcePokemon()!), // Tag not added + console warns if no source
       }),
     );
   }
@@ -835,28 +844,36 @@ export class InfatuatedTag extends BattlerTag {
   lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
     const ret = lapseType !== BattlerTagLapseType.CUSTOM || super.lapse(pokemon, lapseType);
 
-    const phaseManager = globalScene.phaseManager;
-
-    if (ret) {
-      phaseManager.queueMessage(
-        i18next.t("battlerTags:infatuatedLapse", {
-          pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-          sourcePokemonName: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
-        }),
-      );
-      phaseManager.unshiftNew("CommonAnimPhase", pokemon.getBattlerIndex(), undefined, CommonAnim.ATTRACT);
-
-      if (pokemon.randBattleSeedInt(2)) {
-        phaseManager.queueMessage(
-          i18next.t("battlerTags:infatuatedLapseImmobilize", {
-            pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-          }),
-        );
-        (phaseManager.getCurrentPhase() as MovePhase).cancel();
-      }
+    if (!ret) {
+      return false;
     }
 
-    return ret;
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for InfatuatedTag lapse; id: ${this.sourceId}`);
+      return false;
+    }
+
+    const phaseManager = globalScene.phaseManager;
+    phaseManager.queueMessage(
+      i18next.t("battlerTags:infatuatedLapse", {
+        pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
+        sourcePokemonName: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
+      }),
+    );
+    phaseManager.unshiftNew("CommonAnimPhase", pokemon.getBattlerIndex(), undefined, CommonAnim.ATTRACT);
+
+    // 50% chance to disrupt the target's action
+    if (pokemon.randBattleSeedInt(2)) {
+      phaseManager.queueMessage(
+        i18next.t("battlerTags:infatuatedLapseImmobilize", {
+          pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
+        }),
+      );
+      (phaseManager.getCurrentPhase() as MovePhase).cancel();
+    }
+
+    return true;
   }
 
   onRemove(pokemon: Pokemon): void {
@@ -899,6 +916,12 @@ export class SeedTag extends BattlerTag {
   }
 
   onAdd(pokemon: Pokemon): void {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for SeedTag onAdd; id: ${this.sourceId}`);
+      return;
+    }
+
     super.onAdd(pokemon);
 
     globalScene.phaseManager.queueMessage(
@@ -906,47 +929,51 @@ export class SeedTag extends BattlerTag {
         pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
       }),
     );
-    this.sourceIndex = globalScene.getPokemonById(this.sourceId!)!.getBattlerIndex(); // TODO: are those bangs correct?
+    this.sourceIndex = source.getBattlerIndex();
   }
 
   lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
     const ret = lapseType !== BattlerTagLapseType.CUSTOM || super.lapse(pokemon, lapseType);
 
-    if (ret) {
-      const source = pokemon.getOpponents().find(o => o.getBattlerIndex() === this.sourceIndex);
-      if (source) {
-        const cancelled = new BooleanHolder(false);
-        applyAbAttrs("BlockNonDirectDamageAbAttr", pokemon, cancelled);
-
-        if (!cancelled.value) {
-          globalScene.phaseManager.unshiftNew(
-            "CommonAnimPhase",
-            source.getBattlerIndex(),
-            pokemon.getBattlerIndex(),
-            CommonAnim.LEECH_SEED,
-          );
-
-          const damage = pokemon.damageAndUpdate(toDmgValue(pokemon.getMaxHp() / 8), { result: HitResult.INDIRECT });
-          const reverseDrain = pokemon.hasAbilityWithAttr("ReverseDrainAbAttr", false);
-          globalScene.phaseManager.unshiftNew(
-            "PokemonHealPhase",
-            source.getBattlerIndex(),
-            !reverseDrain ? damage : damage * -1,
-            !reverseDrain
-              ? i18next.t("battlerTags:seededLapse", {
-                  pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-                })
-              : i18next.t("battlerTags:seededLapseShed", {
-                  pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-                }),
-            false,
-            true,
-          );
-        }
-      }
+    if (!ret) {
+      return false;
     }
 
-    return ret;
+    // Check which opponent to restore HP to
+    const source = pokemon.getOpponents().find(o => o.getBattlerIndex() === this.sourceIndex);
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for SeedTag lapse; id: ${this.sourceId}`);
+      return false;
+    }
+
+    const cancelled = new BooleanHolder(false);
+    applyAbAttrs("BlockNonDirectDamageAbAttr", pokemon, cancelled);
+
+    if (cancelled.value) {
+      return true;
+    }
+
+    globalScene.phaseManager.unshiftNew(
+      "CommonAnimPhase",
+      source.getBattlerIndex(),
+      pokemon.getBattlerIndex(),
+      CommonAnim.LEECH_SEED,
+    );
+
+    // Damage the target and restore our HP (or take damage in the case of liquid ooze)
+    const damage = pokemon.damageAndUpdate(toDmgValue(pokemon.getMaxHp() / 8), { result: HitResult.INDIRECT });
+    const reverseDrain = pokemon.hasAbilityWithAttr("ReverseDrainAbAttr", false);
+    globalScene.phaseManager.unshiftNew(
+      "PokemonHealPhase",
+      source.getBattlerIndex(),
+      reverseDrain ? -damage : damage,
+      i18next.t(reverseDrain ? "battlerTags:seededLapseShed" : "battlerTags:seededLapse", {
+        pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
+      }),
+      false,
+      true,
+    );
+    return true;
   }
 
   getDescriptor(): string {
@@ -1195,9 +1222,15 @@ export class HelpingHandTag extends BattlerTag {
   }
 
   onAdd(pokemon: Pokemon): void {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for HelpingHandTag onAdd; id: ${this.sourceId}`);
+      return;
+    }
+
     globalScene.phaseManager.queueMessage(
       i18next.t("battlerTags:helpingHandOnAdd", {
-        pokemonNameWithAffix: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
+        pokemonNameWithAffix: getPokemonNameWithAffix(source),
         pokemonName: getPokemonNameWithAffix(pokemon),
       }),
     );
@@ -1219,9 +1252,7 @@ export class IngrainTag extends TrappedTag {
    * @returns boolean True if the tag can be added, false otherwise
    */
   canAdd(pokemon: Pokemon): boolean {
-    const isTrapped = pokemon.getTag(BattlerTagType.TRAPPED);
-
-    return !isTrapped;
+    return !pokemon.getTag(BattlerTagType.TRAPPED);
   }
 
   lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
@@ -1420,15 +1451,22 @@ export abstract class DamagingTrapTag extends TrappedTag {
   }
 }
 
+// TODO: Condense all these tags into 1 singular tag with a modified message func
 export class BindTag extends DamagingTrapTag {
   constructor(turnCount: number, sourceId: number) {
     super(BattlerTagType.BIND, CommonAnim.BIND, turnCount, MoveId.BIND, sourceId);
   }
 
   getTrapMessage(pokemon: Pokemon): string {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for BindTag getTrapMessage; id: ${this.sourceId}`);
+      return "ERROR - CHECK CONSOLE AND REPORT";
+    }
+
     return i18next.t("battlerTags:bindOnTrap", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      sourcePokemonName: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
+      sourcePokemonName: getPokemonNameWithAffix(source),
       moveName: this.getMoveName(),
     });
   }
@@ -1440,9 +1478,16 @@ export class WrapTag extends DamagingTrapTag {
   }
 
   getTrapMessage(pokemon: Pokemon): string {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for WrapTag getTrapMessage; id: ${this.sourceId}`);
+      return "ERROR - CHECK CONSOLE AND REPORT";
+    }
+
     return i18next.t("battlerTags:wrapOnTrap", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      sourcePokemonName: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
+      sourcePokemonName: getPokemonNameWithAffix(source),
+      moveName: this.getMoveName(),
     });
   }
 }
@@ -1473,8 +1518,14 @@ export class ClampTag extends DamagingTrapTag {
   }
 
   getTrapMessage(pokemon: Pokemon): string {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for ClampTag getTrapMessage; id: ${this.sourceId}`);
+      return "ERROR - CHECK CONSOLE AND REPORT ASAP";
+    }
+
     return i18next.t("battlerTags:clampOnTrap", {
-      sourcePokemonNameWithAffix: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
+      sourcePokemonNameWithAffix: getPokemonNameWithAffix(source),
       pokemonName: getPokemonNameWithAffix(pokemon),
     });
   }
@@ -1523,9 +1574,15 @@ export class ThunderCageTag extends DamagingTrapTag {
   }
 
   getTrapMessage(pokemon: Pokemon): string {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for ThunderCageTag getTrapMessage; id: ${this.sourceId}`);
+      return "ERROR - PLEASE REPORT ASAP";
+    }
+
     return i18next.t("battlerTags:thunderCageOnTrap", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      sourcePokemonNameWithAffix: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
+      sourcePokemonNameWithAffix: getPokemonNameWithAffix(source),
     });
   }
 }
@@ -1536,9 +1593,15 @@ export class InfestationTag extends DamagingTrapTag {
   }
 
   getTrapMessage(pokemon: Pokemon): string {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for InfestationTag getTrapMessage; id: ${this.sourceId}`);
+      return "ERROR - CHECK CONSOLE AND REPORT";
+    }
+
     return i18next.t("battlerTags:infestationOnTrap", {
       pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
-      sourcePokemonNameWithAffix: getPokemonNameWithAffix(globalScene.getPokemonById(this.sourceId!) ?? undefined), // TODO: is that bang correct?
+      sourcePokemonNameWithAffix: getPokemonNameWithAffix(source),
     });
   }
 }
@@ -2221,14 +2284,19 @@ export class SaltCuredTag extends BattlerTag {
   }
 
   onAdd(pokemon: Pokemon): void {
-    super.onAdd(pokemon);
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for SaltCureTag onAdd; id: ${this.sourceId}`);
+      return;
+    }
 
+    super.onAdd(pokemon);
     globalScene.phaseManager.queueMessage(
       i18next.t("battlerTags:saltCuredOnAdd", {
         pokemonNameWithAffix: getPokemonNameWithAffix(pokemon),
       }),
     );
-    this.sourceIndex = globalScene.getPokemonById(this.sourceId!)!.getBattlerIndex(); // TODO: are those bangs correct?
+    this.sourceIndex = source.getBattlerIndex();
   }
 
   lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
@@ -2281,8 +2349,14 @@ export class CursedTag extends BattlerTag {
   }
 
   onAdd(pokemon: Pokemon): void {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for CursedTag onAdd; id: ${this.sourceId}`);
+      return;
+    }
+
     super.onAdd(pokemon);
-    this.sourceIndex = globalScene.getPokemonById(this.sourceId!)!.getBattlerIndex(); // TODO: are those bangs correct?
+    this.sourceIndex = source.getBattlerIndex();
   }
 
   lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
@@ -2902,7 +2976,13 @@ export class SubstituteTag extends BattlerTag {
 
   /** Sets the Substitute's HP and queues an on-add battle animation that initializes the Substitute's sprite. */
   onAdd(pokemon: Pokemon): void {
-    this.hp = Math.floor(globalScene.getPokemonById(this.sourceId!)!.getMaxHp() / 4);
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for SubstituteTag onAdd; id: ${this.sourceId}`);
+      return;
+    }
+
+    this.hp = Math.floor(source.getMaxHp() / 4);
     this.sourceInFocus = false;
 
     // Queue battle animation and message
@@ -3182,13 +3262,14 @@ export class ImprisonTag extends MoveRestrictionBattlerTag {
    */
   public override lapse(pokemon: Pokemon, lapseType: BattlerTagLapseType): boolean {
     const source = this.getSourcePokemon();
-    if (source) {
-      if (lapseType === BattlerTagLapseType.PRE_MOVE) {
-        return super.lapse(pokemon, lapseType) && source.isActive(true);
-      }
-      return source.isActive(true);
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for ImprisonTag lapse; id: ${this.sourceId}`);
+      return false;
     }
-    return false;
+    if (lapseType === BattlerTagLapseType.PRE_MOVE) {
+      return super.lapse(pokemon, lapseType) && source.isActive(true);
+    }
+    return source.isActive(true);
   }
 
   /**
@@ -3248,12 +3329,20 @@ export class SyrupBombTag extends BattlerTag {
    * Applies the single-stage speed down to the target Pokemon and decrements the tag's turn count
    * @param pokemon - The target {@linkcode Pokemon}
    * @param _lapseType - N/A
-   * @returns `true` if the `turnCount` is still greater than `0`; `false` if the `turnCount` is `0` or the target or source Pokemon has been removed from the field
+   * @returns Whether the tag should persist (`turnsRemaining > 0` and source still on field)
    */
   override lapse(pokemon: Pokemon, _lapseType: BattlerTagLapseType): boolean {
-    if (this.sourceId && !globalScene.getPokemonById(this.sourceId)?.isActive(true)) {
+    const source = this.getSourcePokemon();
+    if (!source) {
+      console.warn(`Failed to get source Pokemon for SyrupBombTag lapse; id: ${this.sourceId}`);
       return false;
     }
+
+    // Syrup bomb clears immediately if source leaves field/faints
+    if (!source.isActive(true)) {
+      return false;
+    }
+
     // Custom message in lieu of an animation in mainline
     globalScene.phaseManager.queueMessage(
       i18next.t("battlerTags:syrupBombLapse", {
@@ -3270,7 +3359,7 @@ export class SyrupBombTag extends BattlerTag {
       false,
       true,
     );
-    return --this.turnCount > 0;
+    return super.lapse(pokemon, _lapseType);
   }
 }
 
diff --git a/src/data/moves/move.ts b/src/data/moves/move.ts
index f94c59bb463..4caa9f434bb 100644
--- a/src/data/moves/move.ts
+++ b/src/data/moves/move.ts
@@ -6887,12 +6887,12 @@ export class RandomMovesetMoveAttr extends CallMoveAttr {
       // includeParty will be true for Assist, false for Sleep Talk
       let allies: Pokemon[];
       if (this.includeParty) {
-        allies = user.isPlayer() ? globalScene.getPlayerParty().filter(p => p !== user) : globalScene.getEnemyParty().filter(p => p !== user);
+        allies = (user.isPlayer() ? globalScene.getPlayerParty() : globalScene.getEnemyParty()).filter(p => p !== user);
       } else {
         allies = [ user ];
       }
-      const partyMoveset = allies.map(p => p.moveset).flat();
-      const moves = partyMoveset.filter(m => !this.invalidMoves.has(m!.moveId) && !m!.getMove().name.endsWith(" (N)"));
+      const partyMoveset = allies.flatMap(p => p.moveset);
+      const moves = partyMoveset.filter(m => !this.invalidMoves.has(m.moveId) && !m.getMove().name.endsWith(" (N)"));
       if (moves.length === 0) {
         return false;
       }
diff --git a/src/data/mystery-encounters/encounters/dancing-lessons-encounter.ts b/src/data/mystery-encounters/encounters/dancing-lessons-encounter.ts
index c68e395b379..cf24d1dd7e0 100644
--- a/src/data/mystery-encounters/encounters/dancing-lessons-encounter.ts
+++ b/src/data/mystery-encounters/encounters/dancing-lessons-encounter.ts
@@ -328,7 +328,7 @@ export const DancingLessonsEncounter: MysteryEncounter = MysteryEncounterBuilder
       .withOptionPhase(async () => {
         // Show the Oricorio a dance, and recruit it
         const encounter = globalScene.currentBattle.mysteryEncounter!;
-        const oricorio = encounter.misc.oricorioData.toPokemon();
+        const oricorio = encounter.misc.oricorioData.toPokemon() as EnemyPokemon;
         oricorio.passive = true;
 
         // Ensure the Oricorio's moveset gains the Dance move the player used
diff --git a/src/field/pokemon.ts b/src/field/pokemon.ts
index e9cc4f70d70..3080566b815 100644
--- a/src/field/pokemon.ts
+++ b/src/field/pokemon.ts
@@ -4100,7 +4100,7 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   getTag<T extends BattlerTag>(tagType: Constructor<T>): T | undefined;
 
   getTag(tagType: BattlerTagType | Constructor<BattlerTag>): BattlerTag | undefined {
-    return tagType instanceof Function
+    return typeof tagType === "function"
       ? this.summonData.tags.find(t => t instanceof tagType)
       : this.summonData.tags.find(t => t.tagType === tagType);
   }
diff --git a/src/modifier/modifier.ts b/src/modifier/modifier.ts
index 54b7323569a..77d82c2a694 100644
--- a/src/modifier/modifier.ts
+++ b/src/modifier/modifier.ts
@@ -751,7 +751,7 @@ export abstract class PokemonHeldItemModifier extends PersistentModifier {
   }
 
   getPokemon(): Pokemon | undefined {
-    return this.pokemonId ? (globalScene.getPokemonById(this.pokemonId) ?? undefined) : undefined;
+    return globalScene.getPokemonById(this.pokemonId) ?? undefined;
   }
 
   getScoreMultiplier(): number {
diff --git a/test/abilities/unburden.test.ts b/test/abilities/unburden.test.ts
index 6e24e10d168..4bf12d01ad6 100644
--- a/test/abilities/unburden.test.ts
+++ b/test/abilities/unburden.test.ts
@@ -22,10 +22,7 @@ describe("Abilities - Unburden", () => {
    */
   function getHeldItemCount(pokemon: Pokemon): number {
     const stackCounts = pokemon.getHeldItems().map(m => m.getStackCount());
-    if (stackCounts.length) {
-      return stackCounts.reduce((a, b) => a + b);
-    }
-    return 0;
+    return stackCounts.reduce((a, b) => a + b, 0);
   }
 
   beforeAll(() => {
diff --git a/test/field/pokemon-id-checks.test.ts b/test/field/pokemon-id-checks.test.ts
new file mode 100644
index 00000000000..4023b8d73ad
--- /dev/null
+++ b/test/field/pokemon-id-checks.test.ts
@@ -0,0 +1,79 @@
+import type Pokemon from "#app/field/pokemon";
+import { MoveId } from "#enums/move-id";
+import { AbilityId } from "#enums/ability-id";
+import { SpeciesId } from "#enums/species-id";
+import { BattleType } from "#enums/battle-type";
+import { BattlerTagType } from "#enums/battler-tag-type";
+import GameManager from "#test/testUtils/gameManager";
+import Phaser from "phaser";
+import { afterEach, beforeAll, beforeEach, describe, expect, it } from "vitest";
+import { BattlerIndex } from "#enums/battler-index";
+
+describe("Field - Pokemon ID Checks", () => {
+  let phaserGame: Phaser.Game;
+  let game: GameManager;
+
+  beforeAll(() => {
+    phaserGame = new Phaser.Game({
+      type: Phaser.HEADLESS,
+    });
+  });
+
+  afterEach(() => {
+    game.phaseInterceptor.restoreOg();
+  });
+
+  beforeEach(() => {
+    game = new GameManager(phaserGame);
+    game.override
+      .ability(AbilityId.NO_GUARD)
+      .battleStyle("single")
+      .battleType(BattleType.TRAINER)
+      .criticalHits(false)
+      .enemyLevel(100)
+      .enemySpecies(SpeciesId.ARCANINE)
+      .enemyAbility(AbilityId.BALL_FETCH)
+      .enemyMoveset(MoveId.SPLASH);
+  });
+
+  function onlyUnique<T>(array: T[]): T[] {
+    return [...new Set<T>(array)];
+  }
+
+  // TODO: We currently generate IDs as a pure random integer; enable once unique UUIDs are added
+  it.todo("2 Pokemon should not be able to generate with the same ID during 1 encounter", async () => {
+    game.override.battleType(BattleType.TRAINER); // enemy generates 2 mons
+    await game.classicMode.startBattle([SpeciesId.FEEBAS, SpeciesId.ABRA]);
+
+    const ids = (game.scene.getPlayerParty() as Pokemon[]).concat(game.scene.getEnemyParty()).map((p: Pokemon) => p.id);
+    const uniqueIds = onlyUnique(ids);
+
+    expect(ids).toHaveLength(uniqueIds.length);
+  });
+
+  it("should not prevent Battler Tags from triggering if user has PID of 0", async () => {
+    await game.classicMode.startBattle([SpeciesId.TREECKO, SpeciesId.AERODACTYL]);
+
+    const player = game.field.getPlayerPokemon();
+    const enemy = game.field.getEnemyPokemon();
+    // Override player pokemon PID to be 0
+    player.id = 0;
+    expect(player.getTag(BattlerTagType.DESTINY_BOND)).toBeUndefined();
+
+    game.move.use(MoveId.DESTINY_BOND);
+    game.doSelectPartyPokemon(1);
+    await game.move.forceEnemyMove(MoveId.FLAME_WHEEL);
+    await game.setTurnOrder([BattlerIndex.PLAYER, BattlerIndex.ENEMY]);
+    await game.phaseInterceptor.to("MoveEndPhase");
+
+    const dBondTag = player.getTag(BattlerTagType.DESTINY_BOND)!;
+    expect(dBondTag).toBeDefined();
+    expect(dBondTag.sourceId).toBe(0);
+    expect(dBondTag.getSourcePokemon()).toBe(player);
+
+    await game.phaseInterceptor.to("MoveEndPhase");
+
+    expect(player.isFainted()).toBe(true);
+    expect(enemy.isFainted()).toBe(true);
+  });
+});