diff --git a/PkmnLib.Dynamic/Models/Pokemon.cs b/PkmnLib.Dynamic/Models/Pokemon.cs
index 3c3ed98..ddf8544 100644
--- a/PkmnLib.Dynamic/Models/Pokemon.cs
+++ b/PkmnLib.Dynamic/Models/Pokemon.cs
@@ -248,6 +248,9 @@ public interface IPokemon : IScriptSource, IDeepCloneable
     [MustUseReturnValue]
     IItem? RemoveHeldItem();
 
+    /// <summary>
+    /// Whether the held item has been removed for the duration of the battle.
+    /// </summary>
     bool HasItemBeenRemovedForBattle { get; }
 
     /// <summary>
@@ -451,30 +454,45 @@ public interface IPokemon : IScriptSource, IDeepCloneable
 /// </summary>
 public interface IPokemonBattleData : IDeepCloneable
 {
+    /// <summary>
+    /// Sets the battle data of the Pokémon.
+    /// </summary>
+    void SetBattle(IBattle battle, byte sideIndex, uint switchInTurn);
+
+    /// <summary>
+    /// Sets the position of the Pokémon on the field.
+    /// </summary>
+    void SetPosition(byte position);
+
     /// <summary>
     /// The battle the Pokémon is in.
     /// </summary>
-    IBattle Battle { get; internal set; }
+    IBattle Battle { get; }
 
     /// <summary>
     /// The index of the side of the Pokémon
     /// </summary>
-    byte SideIndex { get; internal set; }
+    byte SideIndex { get; }
 
     /// <summary>
     /// The index of the position of the Pokémon on the field
     /// </summary>
-    byte Position { get; internal set; }
+    byte Position { get; }
 
     /// <summary>
     /// A list of opponents the Pokémon has seen this battle.
     /// </summary>
     IReadOnlyList<IPokemon> SeenOpponents { get; }
 
+    /// <summary>
+    /// Sets whether the Pokémon is on the battlefield.
+    /// </summary>
+    void SetOnBattlefield(bool onBattleField);
+
     /// <summary>
     /// Whether the Pokémon is on the battlefield.
     /// </summary>
-    bool IsOnBattlefield { get; internal set; }
+    bool IsOnBattlefield { get; }
 
     /// <summary>
     /// Adds an opponent to the list of seen opponents.
@@ -494,8 +512,11 @@ public interface IPokemonBattleData : IDeepCloneable
     /// <summary>
     /// The turn the Pokémon switched in.
     /// </summary>
-    uint SwitchInTurn { get; internal set; }
+    uint SwitchInTurn { get; }
 
+    /// <summary>
+    /// The number of turns the Pokémon has been on the field.
+    /// </summary>
     uint TurnsOnField { get; }
 
     /// <summary>
@@ -516,7 +537,7 @@ public interface IPokemonBattleData : IDeepCloneable
     /// <summary>
     /// The last move choice executed by the Pokémon.
     /// </summary>
-    IMoveChoice? LastMoveChoice { get; internal set; }
+    IMoveChoice? LastMoveChoice { get; set; }
 }
 
 /// <inheritdoc cref="IPokemon"/>
@@ -1315,9 +1336,7 @@ public class PokemonImpl : ScriptSource, IPokemon
     {
         if (BattleData is not null)
         {
-            BattleData.Battle = battle;
-            BattleData.SideIndex = sideIndex;
-            BattleData.SwitchInTurn = battle.CurrentTurnNumber;
+            BattleData.SetBattle(battle, sideIndex, battle.CurrentTurnNumber);
         }
         else
         {
@@ -1340,7 +1359,7 @@ public class PokemonImpl : ScriptSource, IPokemon
     {
         if (BattleData is not null)
         {
-            BattleData.IsOnBattlefield = onBattleField;
+            BattleData.SetOnBattlefield(onBattleField);
             if (!onBattleField)
             {
                 Volatile.Clear();
@@ -1356,10 +1375,7 @@ public class PokemonImpl : ScriptSource, IPokemon
     /// <inheritdoc />
     public void SetBattleSidePosition(byte position)
     {
-        if (BattleData is not null)
-        {
-            BattleData.Position = position;
-        }
+        BattleData?.SetPosition(position);
     }
 
     /// <inheritdoc />
@@ -1494,6 +1510,20 @@ public class PokemonBattleDataImpl : IPokemonBattleData
         OriginalForm = originalForm;
     }
 
+    /// <inheritdoc />
+    public void SetBattle(IBattle battle, byte sideIndex, uint switchInTurn)
+    {
+        Battle = battle;
+        SideIndex = sideIndex;
+        SwitchInTurn = switchInTurn;
+    }
+
+    /// <inheritdoc />
+    public void SetPosition(byte position)
+    {
+        Position = position;
+    }
+
     /// <inheritdoc />
     public IBattle Battle { get; set; }
 
@@ -1508,6 +1538,12 @@ public class PokemonBattleDataImpl : IPokemonBattleData
     /// <inheritdoc />
     public IReadOnlyList<IPokemon> SeenOpponents => _seenOpponents;
 
+    /// <inheritdoc />
+    public void SetOnBattlefield(bool onBattleField)
+    {
+        IsOnBattlefield = onBattleField;
+    }
+
     /// <inheritdoc />
     public bool IsOnBattlefield { get; set; }
 
diff --git a/Plugins/PkmnLib.Plugin.Gen7.Tests/Scripts/Abilities/AftermathTests.cs b/Plugins/PkmnLib.Plugin.Gen7.Tests/Scripts/Abilities/AftermathTests.cs
new file mode 100644
index 0000000..e6f54fe
--- /dev/null
+++ b/Plugins/PkmnLib.Plugin.Gen7.Tests/Scripts/Abilities/AftermathTests.cs
@@ -0,0 +1,367 @@
+using PkmnLib.Dynamic.Events;
+using PkmnLib.Dynamic.Models;
+using PkmnLib.Dynamic.ScriptHandling;
+using PkmnLib.Plugin.Gen7.Scripts.Abilities;
+using PkmnLib.Static.Species;
+using PkmnLib.Static.Utils;
+
+namespace PkmnLib.Plugin.Gen7.Tests.Scripts.Abilities;
+
+/// <summary>
+/// Tests for the Aftermath ability.
+/// </summary>
+public class AftermathTests
+{
+    /// <summary>
+    /// Creates a fully mocked test setup for Aftermath tests.
+    /// </summary>
+    private static (Aftermath aftermath, IExecutingMove move, IPokemon target, IPokemon user, EventHook eventHook,
+        IBattle battle) CreateFullTestSetup(bool isContact, uint userMaxHealth = 100)
+    {
+        var aftermath = new Aftermath();
+        var move = Substitute.For<IExecutingMove>();
+        var target = Substitute.For<IPokemon>();
+        var hitData = Substitute.For<IHitData>();
+        hitData.IsContact.Returns(isContact);
+        move.GetHitData(target, 0).Returns(hitData);
+
+        var eventHook = new EventHook();
+        var battle = Substitute.For<IBattle>();
+        battle.EventHook.Returns(eventHook);
+
+        // Setup empty sides by default (no Damp on field)
+        var side = Substitute.For<IBattleSide>();
+        side.Pokemon.Returns(new List<IPokemon?>());
+        battle.Sides.Returns(new[] { side });
+
+        var battleData = Substitute.For<IPokemonBattleData>();
+        battleData.Battle.Returns(battle);
+
+        var user = Substitute.For<IPokemon>();
+        user.IsUsable.Returns(true);
+        user.MaxHealth.Returns(userMaxHealth);
+
+        // Configure BattleData return value using NSubstitute's callback pattern
+        // First return null to suppress auto-substitution, then configure actual value
+        user.BattleData.Returns(battleData);
+
+        move.User.Returns(user);
+
+        return (aftermath, move, target, user, eventHook, battle);
+    }
+
+    /// <summary>
+    /// Helper to extract the damage amount from a substitute's received Damage calls.
+    /// </summary>
+    private static uint GetDamageDealt(IPokemon user)
+    {
+        var damageCall = user.ReceivedCalls().FirstOrDefault(c => c.GetMethodInfo().Name == "Damage");
+        return damageCall != null ? (uint)damageCall.GetArguments()[0]! : 0;
+    }
+
+    /// <summary>
+    /// Helper to extract the damage source from a substitute's received Damage calls.
+    /// </summary>
+    private static DamageSource? GetDamageSource(IPokemon user)
+    {
+        var damageCall = user.ReceivedCalls().FirstOrDefault(c => c.GetMethodInfo().Name == "Damage");
+        return damageCall != null ? (DamageSource)damageCall.GetArguments()[1]! : null;
+    }
+
+    /// <summary>
+    /// Bulbapedia: "When a Pokémon with this Ability faints from damage caused by a move that makes contact,
+    /// the attacking Pokémon takes damage equal to ¼ of its own maximum HP."
+    /// This test verifies that contact moves trigger the ability and deal 1/4 max HP damage.
+    /// </summary>
+    [Test]
+    public async Task OnFaint_ContactMove_DealsQuarterMaxHpDamage()
+    {
+        // Arrange
+        var (aftermath, move, target, user, _, _) = CreateFullTestSetup(true, 100);
+
+        // Act
+        aftermath.OnIncomingHit(move, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert - Should deal 25 damage (1/4 of 100)
+        await Assert.That(GetDamageDealt(user)).IsEqualTo(25u);
+    }
+
+    /// <summary>
+    /// Bulbapedia: "the attacking Pokémon takes damage equal to ¼ of its own maximum HP."
+    /// Tests various max HP values to ensure proper integer division.
+    /// </summary>
+    [Test, Arguments(100u, 25u), Arguments(200u, 50u), Arguments(44u, 11u), Arguments(99u, 24u), Arguments(1u, 0u)]
+    public async Task OnFaint_ContactMove_DamageCalculation(uint maxHealth, uint expectedDamage)
+    {
+        // Arrange
+        var (aftermath, move, target, user, _, _) = CreateFullTestSetup(true, maxHealth);
+
+        // Act
+        aftermath.OnIncomingHit(move, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert
+        await Assert.That(GetDamageDealt(user)).IsEqualTo(expectedDamage);
+    }
+
+    /// <summary>
+    /// Bulbapedia: Aftermath triggers "from damage caused by a move that makes contact".
+    /// Non-contact moves should not trigger the ability.
+    /// </summary>
+    [Test]
+    public async Task OnFaint_NonContactMove_DoesNotDealDamage()
+    {
+        // Arrange
+        var (aftermath, move, target, user, _, _) = CreateFullTestSetup(false);
+
+        // Act
+        aftermath.OnIncomingHit(move, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert - Damage should never be called
+        await Assert.That(user.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Damage")).IsFalse();
+    }
+
+    /// <summary>
+    /// Bulbapedia: Aftermath triggers when the Pokémon "faints from damage".
+    /// If the faint is not from move damage, the ability should not trigger.
+    /// </summary>
+    [Test]
+    public async Task OnFaint_NotFromMoveDamage_DoesNotTrigger()
+    {
+        // Arrange
+        var (aftermath, move, target, user, _, _) = CreateFullTestSetup(true);
+
+        aftermath.OnIncomingHit(move, target, 0);
+
+        // Act - Faint from non-move damage source
+        aftermath.OnFaint(target, DamageSource.Misc);
+
+        // Assert - Damage should never be called
+        await Assert.That(user.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Damage")).IsFalse();
+    }
+
+    /// <summary>
+    /// Bulbapedia: "the attacking Pokémon takes damage".
+    /// If the attacker has already fainted (IsUsable = false), no damage should be dealt.
+    /// </summary>
+    [Test]
+    public async Task OnFaint_AttackerNotUsable_DoesNotDealDamage()
+    {
+        // Arrange
+        var aftermath = new Aftermath();
+        var move = Substitute.For<IExecutingMove>();
+        var target = Substitute.For<IPokemon>();
+        var hitData = Substitute.For<IHitData>();
+        hitData.IsContact.Returns(true);
+        move.GetHitData(target, 0).Returns(hitData);
+
+        var user = Substitute.For<IPokemon>();
+        user.IsUsable.Returns(false); // Attacker already fainted
+        move.User.Returns(user);
+
+        // Act
+        aftermath.OnIncomingHit(move, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert - Damage should never be called because IsUsable check fails
+        await Assert.That(user.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Damage")).IsFalse();
+    }
+
+    /// <summary>
+    /// Bulbapedia: "the attacking Pokémon takes damage".
+    /// If the attacker has no battle data, no damage should be dealt.
+    /// </summary>
+    [Test]
+    public async Task OnFaint_AttackerHasNoBattleData_DoesNotDealDamage()
+    {
+        // Arrange
+        var aftermath = new Aftermath();
+        var move = Substitute.For<IExecutingMove>();
+        var target = Substitute.For<IPokemon>();
+        var hitData = Substitute.For<IHitData>();
+        hitData.IsContact.Returns(true);
+        move.GetHitData(target, 0).Returns(hitData);
+
+        var user = Substitute.For<IPokemon>();
+        user.IsUsable.Returns(true);
+        user.BattleData.Returns((IPokemonBattleData?)null);
+        move.User.Returns(user);
+
+        // Act
+        aftermath.OnIncomingHit(move, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert - Damage should never be called because BattleData is null
+        await Assert.That(user.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Damage")).IsFalse();
+    }
+
+    /// <summary>
+    /// Technical test: Verifies OnFaint handles the case where no attack was received.
+    /// </summary>
+    [Test]
+    public void OnFaint_NoLastAttackStored_DoesNotThrow()
+    {
+        // Arrange
+        var aftermath = new Aftermath();
+        var target = Substitute.For<IPokemon>();
+
+        // Act & Assert - Should not throw when _lastAttack is null
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+    }
+
+    /// <summary>
+    /// Bulbapedia: Aftermath triggers on "a move that makes contact".
+    /// When multiple hits occur, only the last hit determines whether Aftermath triggers.
+    /// This tests that a contact hit after a non-contact hit will trigger.
+    /// </summary>
+    [Test]
+    public async Task OnIncomingHit_MultipleHits_LastContactHitTriggers()
+    {
+        // Arrange
+        var aftermath = new Aftermath();
+        var target = Substitute.For<IPokemon>();
+        var battle = Substitute.For<IBattle>();
+        var eventHook = new EventHook();
+        battle.EventHook.Returns(eventHook);
+
+        // Setup empty sides (no Damp on field)
+        var side = Substitute.For<IBattleSide>();
+        side.Pokemon.Returns(new List<IPokemon?>());
+        battle.Sides.Returns(new[] { side });
+
+        var battleData = Substitute.For<IPokemonBattleData>();
+        battleData.Battle.Returns(battle);
+
+        // First hit - non-contact
+        var move1 = Substitute.For<IExecutingMove>();
+        var hitData1 = Substitute.For<IHitData>();
+        hitData1.IsContact.Returns(false);
+        move1.GetHitData(target, 0).Returns(hitData1);
+
+        // Second hit - contact (should be stored and trigger)
+        var move2 = Substitute.For<IExecutingMove>();
+        var hitData2 = Substitute.For<IHitData>();
+        hitData2.IsContact.Returns(true);
+        move2.GetHitData(target, 0).Returns(hitData2);
+        var user = Substitute.For<IPokemon>();
+        user.IsUsable.Returns(true);
+        user.BattleData.Returns(battleData);
+        user.MaxHealth.Returns(100u);
+        move2.User.Returns(user);
+
+        // Act
+        aftermath.OnIncomingHit(move1, target, 0);
+        aftermath.OnIncomingHit(move2, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert - Should deal 25 damage from the last contact hit
+        await Assert.That(GetDamageDealt(user)).IsEqualTo(25u);
+    }
+
+    /// <summary>
+    /// Bulbapedia: Aftermath triggers on "a move that makes contact".
+    /// When the last hit is non-contact, Aftermath should not trigger.
+    /// </summary>
+    [Test]
+    public async Task OnIncomingHit_MultipleHits_LastNonContactDoesNotTrigger()
+    {
+        // Arrange
+        var aftermath = new Aftermath();
+        var target = Substitute.For<IPokemon>();
+
+        // First hit - contact
+        var move1 = Substitute.For<IExecutingMove>();
+        var hitData1 = Substitute.For<IHitData>();
+        hitData1.IsContact.Returns(true);
+        move1.GetHitData(target, 0).Returns(hitData1);
+
+        // Second hit - non-contact (overwrites, sets to null)
+        var move2 = Substitute.For<IExecutingMove>();
+        var hitData2 = Substitute.For<IHitData>();
+        hitData2.IsContact.Returns(false);
+        move2.GetHitData(target, 0).Returns(hitData2);
+
+        // Act
+        aftermath.OnIncomingHit(move1, target, 0);
+        aftermath.OnIncomingHit(move2, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert - Neither move's User should be accessed (_lastAttack is null)
+        await Assert.That(move1.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "get_User")).IsFalse();
+        await Assert.That(move2.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "get_User")).IsFalse();
+    }
+
+    /// <summary>
+    /// Bulbapedia: "When a Pokémon with this Ability faints..."
+    /// Verifies that the AbilityTriggerEvent is fired when Aftermath triggers.
+    /// </summary>
+    [Test]
+    public async Task OnFaint_ContactMove_FiresAbilityTriggerEvent()
+    {
+        // Arrange
+        var (aftermath, move, target, user, eventHook, _) = CreateFullTestSetup(true);
+        AbilityTriggerEvent? capturedEvent = null;
+        eventHook.Handler += (sender, args) =>
+        {
+            if (args is AbilityTriggerEvent ate)
+                capturedEvent = ate;
+        };
+
+        // Act
+        aftermath.OnIncomingHit(move, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert - AbilityTriggerEvent should be fired with the target (Aftermath owner)
+        await Assert.That(capturedEvent).IsNotNull();
+        await Assert.That(capturedEvent!.Pokemon).IsEqualTo(target);
+    }
+
+    /// <summary>
+    /// Bulbapedia: "the attacking Pokémon takes damage equal to ¼ of its own maximum HP."
+    /// Verifies that the damage source is DamageSource.Misc (not MoveDamage).
+    /// </summary>
+    [Test]
+    public async Task OnFaint_ContactMove_UsesMiscDamageSource()
+    {
+        // Arrange
+        var (aftermath, move, target, user, _, _) = CreateFullTestSetup(true);
+
+        // Act
+        aftermath.OnIncomingHit(move, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert
+        await Assert.That(GetDamageSource(user)).IsEqualTo(DamageSource.Misc);
+    }
+
+    /// <summary>
+    /// Bulbapedia: Aftermath does not activate "if a Pokémon with Damp is on the field".
+    /// This test verifies that Aftermath is suppressed when any Pokémon on the field has Damp.
+    /// </summary>
+    [Test]
+    public async Task OnFaint_DampOnField_DoesNotTrigger()
+    {
+        // Arrange
+        var (aftermath, move, target, user, _, battle) = CreateFullTestSetup(true, 100);
+
+        // Create a Pokemon with Damp ability on the field
+        var dampPokemon = Substitute.For<IPokemon>();
+        var dampAbility = Substitute.For<IAbility>();
+        dampAbility.Name.Returns(new StringKey("damp"));
+        dampPokemon.ActiveAbility.Returns(dampAbility);
+
+        // Update battle sides to include the Damp Pokemon
+        var side = Substitute.For<IBattleSide>();
+        side.Pokemon.Returns(new List<IPokemon?> { dampPokemon });
+        battle.Sides.Returns(new[] { side });
+
+        // Act
+        aftermath.OnIncomingHit(move, target, 0);
+        aftermath.OnFaint(target, DamageSource.MoveDamage);
+
+        // Assert - Damage should never be called because Damp prevents Aftermath
+        await Assert.That(user.ReceivedCalls().Any(c => c.GetMethodInfo().Name == "Damage")).IsFalse();
+    }
+}
\ No newline at end of file
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Aftermath.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Aftermath.cs
index 07b0c8e..2fdfc50 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Aftermath.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Aftermath.cs
@@ -9,12 +9,14 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Abilities;
 [Script(ScriptCategory.Ability, "aftermath")]
 public class Aftermath : Script, IScriptOnIncomingHit, IScriptOnFaint
 {
+    private static readonly StringKey DampAbilityName = new("damp");
+
     private IExecutingMove? _lastAttack;
 
     /// <inheritdoc />
     public void OnIncomingHit(IExecutingMove move, IPokemon target, byte hit)
     {
-        _lastAttack = !move.GetHitData(target, hit).IsContact ? move : null;
+        _lastAttack = move.GetHitData(target, hit).IsContact ? move : null;
     }
 
     /// <inheritdoc />
@@ -29,8 +31,16 @@ public class Aftermath : Script, IScriptOnIncomingHit, IScriptOnFaint
             return;
         if (user.BattleData is null)
             return;
+
+        // Aftermath does not trigger if a Pokémon with Damp is on the field
+        var battle = user.BattleData.Battle;
+        var hasDamp = battle.Sides.SelectMany(side => side.Pokemon).WhereNotNull()
+            .Any(p => p.ActiveAbility?.Name == DampAbilityName);
+        if (hasDamp)
+            return;
+
         EventBatchId eventBatchId = new();
-        user.BattleData.Battle.EventHook.Invoke(new AbilityTriggerEvent(pokemon)
+        battle.EventHook.Invoke(new AbilityTriggerEvent(pokemon)
         {
             BatchId = eventBatchId,
         });