diff --git a/PkmnLib.Dynamic/ScriptHandling/Script.cs b/PkmnLib.Dynamic/ScriptHandling/Script.cs
index 410d0c5..297f04e 100644
--- a/PkmnLib.Dynamic/ScriptHandling/Script.cs
+++ b/PkmnLib.Dynamic/ScriptHandling/Script.cs
@@ -774,7 +774,7 @@ public abstract class Script : IDeepCloneable
     /// <summary>
     /// This function allows a script to prevent a Pokémon from being affected by a volatile status condition.
     /// </summary>
-    public virtual void PreventVolatileAdd(Script script, ref bool preventVolatileAdd)
+    public virtual void PreventVolatileAdd(IScriptSource parent, Script script, ref bool preventVolatileAdd)
     {
     }
 
diff --git a/PkmnLib.Dynamic/ScriptHandling/ScriptSet.cs b/PkmnLib.Dynamic/ScriptHandling/ScriptSet.cs
index 135bf91..5ab6681 100644
--- a/PkmnLib.Dynamic/ScriptHandling/ScriptSet.cs
+++ b/PkmnLib.Dynamic/ScriptHandling/ScriptSet.cs
@@ -86,7 +86,7 @@ public interface IScriptSet : IEnumerable<ScriptContainer>
 /// <inheritdoc cref="IScriptSet"/>
 public class ScriptSet : IScriptSet
 {
-    private IScriptSource _source;
+    private readonly IScriptSource _source;
 
     private readonly List<ScriptContainer> _scripts = [];
 
@@ -108,7 +108,7 @@ public class ScriptSet : IScriptSet
         if (!forceAdd)
         {
             var preventVolatileAdd = false;
-            _source.RunScriptHook(x => x.PreventVolatileAdd(script, ref preventVolatileAdd));
+            _source.RunScriptHook(x => x.PreventVolatileAdd(_source, script, ref preventVolatileAdd));
             if (preventVolatileAdd)
                 return null;
         }
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/InnerFocus.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/InnerFocus.cs
index 1bdd4c7..d772b58 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/InnerFocus.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/InnerFocus.cs
@@ -21,7 +21,7 @@ public class InnerFocus : Script
     }
 
     /// <inheritdoc />
-    public override void PreventVolatileAdd(Script script, ref bool preventVolatileAdd)
+    public override void PreventVolatileAdd(IScriptSource parent, Script script, ref bool preventVolatileAdd)
     {
         if (script is not FlinchEffect)
             return;
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Oblivious.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Oblivious.cs
index 7a3f8c0..7955420 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Oblivious.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/Oblivious.cs
@@ -11,7 +11,7 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Abilities;
 public class Oblivious : Script
 {
     /// <inheritdoc />
-    public override void PreventVolatileAdd(Script script, ref bool preventVolatileAdd)
+    public override void PreventVolatileAdd(IScriptSource parent, Script script, ref bool preventVolatileAdd)
     {
         preventVolatileAdd = script switch
         {
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/OwnTempo.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/OwnTempo.cs
index cf61eb8..07931bb 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/OwnTempo.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Abilities/OwnTempo.cs
@@ -9,7 +9,7 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Abilities;
 public class OwnTempo : Script
 {
     /// <inheritdoc />
-    public override void PreventVolatileAdd(Script script, ref bool preventVolatileAdd)
+    public override void PreventVolatileAdd(IScriptSource parent, Script script, ref bool preventVolatileAdd)
     {
         if (script is Pokemon.Confusion)
             preventVolatileAdd = true;
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Side/SafeguardEffect.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Side/SafeguardEffect.cs
index 590d3b5..5c1f12f 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Side/SafeguardEffect.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Side/SafeguardEffect.cs
@@ -12,7 +12,7 @@ public class SafeguardEffect : Script
     }
 
     /// <inheritdoc />
-    public override void PreventVolatileAdd(Script script, ref bool preventVolatileAdd)
+    public override void PreventVolatileAdd(IScriptSource parent, Script script, ref bool preventVolatileAdd)
     {
         if (script.Category == ScriptCategory.Pokemon && script.Name == ScriptUtils.ResolveName<Confusion>())
             preventVolatileAdd = true;
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/ElectricTerrain.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/ElectricTerrain.cs
index 8d737d1..2c2d6f8 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/ElectricTerrain.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/ElectricTerrain.cs
@@ -3,5 +3,36 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Terrain;
 [Script(ScriptCategory.Terrain, "electric_terrain")]
 public class ElectricTerrain : Script
 {
-    // TODO: Implement Terrain
+    private static bool IsAffectedByTerrain(IPokemon pokemon) =>
+        !pokemon.IsFloating;
+
+    /// <inheritdoc />
+    public override void ChangeBasePower(IExecutingMove move, IPokemon target, byte hit, ref ushort basePower)
+    {
+        if (!IsAffectedByTerrain(move.User))
+            return;
+        var type = move.GetHitData(target, hit).Type;
+        if (type?.Name == "electric")
+            basePower = basePower.MultiplyOrMax(1.5f);
+    }
+
+    /// <inheritdoc />
+    public override void PreventStatusChange(IPokemon pokemon, StringKey status, bool selfInflicted,
+        ref bool preventStatus)
+    {
+        if (!IsAffectedByTerrain(pokemon))
+            return;
+        if (status == ScriptUtils.ResolveName<Status.Sleep>())
+            preventStatus = true;
+    }
+
+    /// <inheritdoc />
+    public override void PreventVolatileAdd(IScriptSource parent, Script script, ref bool preventVolatileAdd)
+    {
+        if (parent is IPokemon pokemon && !IsAffectedByTerrain(pokemon))
+            return;
+
+        if (script is Pokemon.YawnEffect)
+            preventVolatileAdd = true;
+    }
 }
\ No newline at end of file
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/GrassyTerrain.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/GrassyTerrain.cs
index d82c38a..1174d52 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/GrassyTerrain.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/GrassyTerrain.cs
@@ -3,5 +3,46 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Terrain;
 [Script(ScriptCategory.Terrain, "grassy_terrain")]
 public class GrassyTerrain : Script
 {
-    // TODO: Implement Terrain
+    private static bool IsAffectedByTerrain(IPokemon pokemon) =>
+        !pokemon.IsFloating;
+
+    /// <inheritdoc />
+    public override void ChangeBasePower(IExecutingMove move, IPokemon target, byte hit, ref ushort basePower)
+    {
+        // It boosts the power of Grass-type moves used by affected Pokémon by 50% (regardless of whether the target of
+        // the move is affected by Grassy Terrain).
+        if (IsAffectedByTerrain(move.User))
+        {
+            var type = move.GetHitData(target, hit).Type;
+            if (type?.Name == "grass")
+            {
+                basePower = basePower.MultiplyOrMax(1.5f);
+            }
+        }
+
+        // The power of Bulldoze, Earthquake, and Magnitude is halved against affected targets (regardless of whether the
+        // user of the move is affected by Grassy Terrain).
+        if (IsAffectedByTerrain(target))
+        {
+            var moveName = move.UseMove.Name;
+            if (moveName == "bulldoze" || moveName == "earthquake" || moveName == "magnitude")
+            {
+                basePower /= 2;
+            }
+        }
+    }
+
+    /// <inheritdoc />
+    public override void OnEndTurn(IScriptSource owner, IBattle battle)
+    {
+        // At the end of each turn, Grassy Terrain restores 1/16 of the maximum HP of each affected Pokémon.
+        foreach (var pokemon in battle.Sides.SelectMany(x => x.Pokemon).WhereNotNull())
+        {
+            if (!IsAffectedByTerrain(pokemon) || pokemon.IsFainted)
+                continue;
+
+            var healing = pokemon.MaxHealth / 16f;
+            pokemon.Heal((uint)healing);
+        }
+    }
 }
\ No newline at end of file
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/MistyTerrain.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/MistyTerrain.cs
index 029ca0a..86ee828 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/MistyTerrain.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/MistyTerrain.cs
@@ -3,5 +3,26 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Terrain;
 [Script(ScriptCategory.Terrain, "misty_terrain")]
 public class MistyTerrain : Script
 {
-    // TODO: Implement Terrain
+    private static bool IsAffectedByTerrain(IPokemon pokemon) =>
+        !pokemon.IsFloating;
+
+    /// <inheritdoc />
+    public override void ChangeBasePower(IExecutingMove move, IPokemon target, byte hit, ref ushort basePower)
+    {
+        if (!IsAffectedByTerrain(target))
+            return;
+        if (move.GetHitData(target, hit).Type?.Name == "dragon")
+        {
+            basePower /= 2;
+        }
+    }
+
+    /// <inheritdoc />
+    public override void PreventStatusChange(IPokemon pokemon, StringKey status, bool selfInflicted,
+        ref bool preventStatus)
+    {
+        if (!IsAffectedByTerrain(pokemon))
+            return;
+        preventStatus = true;
+    }
 }
\ No newline at end of file
diff --git a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/PsychicTerrain.cs b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/PsychicTerrain.cs
index 489d8db..62cb6f9 100644
--- a/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/PsychicTerrain.cs
+++ b/Plugins/PkmnLib.Plugin.Gen7/Scripts/Terrain/PsychicTerrain.cs
@@ -3,5 +3,34 @@ namespace PkmnLib.Plugin.Gen7.Scripts.Terrain;
 [Script(ScriptCategory.Terrain, "psychic_terrain")]
 public class PsychicTerrain : Script
 {
-    // TODO: Implement Terrain
+    private static bool IsAffectedByTerrain(IPokemon pokemon) =>
+        !pokemon.IsFloating;
+
+    /// <inheritdoc />
+    public override void ChangeBasePower(IExecutingMove move, IPokemon target, byte hit, ref ushort basePower)
+    {
+        if (!IsAffectedByTerrain(move.User))
+            return;
+
+        // It boosts the power of Psychic-type moves used by affected Pokémon by 50% (regardless of whether the target of
+        // the move is affected by Psychic Terrain).
+        var type = move.GetHitData(target, hit).Type;
+        if (type?.Name == "psychic")
+        {
+            basePower = basePower.MultiplyOrMax(1.5f);
+        }
+    }
+
+    /// <inheritdoc />
+    public override void IsInvulnerableToMove(IExecutingMove move, IPokemon target, ref bool invulnerable)
+    {
+        if (!IsAffectedByTerrain(target))
+            return;
+
+        // Psychic Terrain prevents priority moves from affecting affected Pokémon.
+        if (move.MoveChoice.Priority > 0)
+        {
+            invulnerable = true;
+        }
+    }
 }
\ No newline at end of file