diff --git a/pflib-net/characters/PlayerCharacter.cs b/pflib-net/characters/PlayerCharacter.cs
index 308c38c..b6ad0bb 100644
--- a/pflib-net/characters/PlayerCharacter.cs
+++ b/pflib-net/characters/PlayerCharacter.cs
@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using pflib_net.characters.internals.proficiencies;
 using pflib_net.characters.internals.stats;
+using pflib_net.conditions;
 using pflib_net.damage;
 
 namespace pflib_net.characters;
@@ -14,6 +15,7 @@ public class PlayerCharacter : ICharacter
     private ISet<string> Immunities { get; }
     private Dictionary<string, int> Resistances { get; }
     private Dictionary<string, int> Weaknesses { get; }
+    private IEnumerable<ICondition>? Conditions { get; set; } = null;
 
     public PlayerCharacter(
         int hp,
diff --git a/pflib-net/conditions/ICondition.cs b/pflib-net/conditions/ICondition.cs
new file mode 100644
index 0000000..87869c4
--- /dev/null
+++ b/pflib-net/conditions/ICondition.cs
@@ -0,0 +1,9 @@
+using pflib_net.characters;
+using pflib_net.effects;
+
+namespace pflib_net.conditions;
+
+public interface ICondition
+{
+    public ISet<IEffect> GetEffects(ICharacter character);
+}
\ No newline at end of file
diff --git a/pflib-net/dice/Dice.cs b/pflib-net/dice/Dice.cs
index 723283a..404dafe 100644
--- a/pflib-net/dice/Dice.cs
+++ b/pflib-net/dice/Dice.cs
@@ -1,21 +1,43 @@
 namespace pflib_net.dice;
 
-public struct Dice
+public class Dice
 {
+    private int _keepHighest;
+    private int _keepLowest;
     private int Count { get; set; }
     private int Size { get; set; }
-    private int KeepHighest { get; set; }
-    private int KeepLowest { get; set; }
+
+    private int KeepHighest
+    {
+        get => _keepHighest;
+        set
+        {
+            if (value > 0 && KeepLowest > 0)
+            {
+                throw new InvalidOperationException("Cannot set keepHighest and keepLowest at the same time");
+            }
+            _keepHighest = value;
+        }
+    }
+
+    private int KeepLowest
+    {
+        get => _keepLowest;
+        set
+        {
+            if (value > 0 && KeepHighest > 0)
+            {
+                throw new InvalidOperationException("Cannot set keepHighest and keepLowest at the same time");
+            }
+
+            _keepLowest = value;
+        }
+    }
     private int Add { get; set; }
     private static readonly Random Random = new();
 
     public Dice(int size, int count = 1, int keepHighest = 0, int keepLowest = 0, int add = 0)
     {
-        if (keepHighest > 0 && keepLowest > 0)
-        {
-            throw new InvalidOperationException("Cannot set keepHighest and keepLowest at the same time");
-        }
-        
         Count = count;
         Size = size;
         KeepHighest = keepHighest;
@@ -25,22 +47,12 @@ public struct Dice
 
     public Dice Kh(int keepHighest)
     {
-        if (KeepLowest > 0)
-        {
-            throw new InvalidOperationException("Cannot set keepHighest and keepLowest in the same roll");
-        }
-
         KeepHighest = keepHighest;
         return this;
     }
 
     public Dice Kl(int keepLowest)
     {
-        if (KeepHighest > 0)
-        {
-            throw new InvalidOperationException("Cannot set keepHighest and keepLowest in the same roll");
-        }
-
         KeepLowest = keepLowest;
         return this;
     }
diff --git a/pflib-net/effects/IEffect.cs b/pflib-net/effects/IEffect.cs
new file mode 100644
index 0000000..95e83f9
--- /dev/null
+++ b/pflib-net/effects/IEffect.cs
@@ -0,0 +1,6 @@
+namespace pflib_net.effects;
+
+public interface IEffect
+{
+    public string Reason { get; }
+}
\ No newline at end of file
diff --git a/pflib-net/effects/implementation/ConditionEffect.cs b/pflib-net/effects/implementation/ConditionEffect.cs
new file mode 100644
index 0000000..a7aecc3
--- /dev/null
+++ b/pflib-net/effects/implementation/ConditionEffect.cs
@@ -0,0 +1,24 @@
+using pflib_net.conditions;
+
+namespace pflib_net.effects.implementation;
+
+public readonly struct ConditionEffect: IEffect
+{
+    private readonly ICondition _condition;
+    private readonly string _reason;
+    public ICondition Condition
+    {
+        get => _condition;
+    }
+    public string Reason
+    {
+        get => _reason;
+        init => _reason = value;
+    }
+    
+    public ConditionEffect(ICondition condition, string reason)
+    {
+        _condition = condition;
+        _reason = reason;
+    }
+}
\ No newline at end of file
diff --git a/pflib-net/effects/implementation/ImmunityEffect.cs b/pflib-net/effects/implementation/ImmunityEffect.cs
new file mode 100644
index 0000000..a5474a6
--- /dev/null
+++ b/pflib-net/effects/implementation/ImmunityEffect.cs
@@ -0,0 +1,14 @@
+namespace pflib_net.effects.implementation;
+
+public readonly struct ImmunityEffect: IEffect
+{
+    public ImmunityEffect(string tag, string reason)
+    {
+        Tag = tag;
+        Reason = reason;
+    }
+
+    public string Tag { get; }
+
+    public string Reason { get; }
+}
\ No newline at end of file
diff --git a/pflib-net/effects/implementation/ModifierEffect.cs b/pflib-net/effects/implementation/ModifierEffect.cs
new file mode 100644
index 0000000..95dbd71
--- /dev/null
+++ b/pflib-net/effects/implementation/ModifierEffect.cs
@@ -0,0 +1,19 @@
+namespace pflib_net.effects.implementation;
+
+public readonly struct ModifierEffect: IEffect
+{
+    public ModifierEffect(string tag, string reason, int value, string? type)
+    {
+        Tag = tag;
+        Reason = reason;
+        Value = value;
+        Type = type;
+    }
+
+    public string Tag { get; }
+
+    public string Reason { get; }
+
+    public string? Type { get; }
+    public int Value { get; }
+}
\ No newline at end of file
diff --git a/pflib-net/effects/implementation/ResistanceEffect.cs b/pflib-net/effects/implementation/ResistanceEffect.cs
new file mode 100644
index 0000000..7cee82e
--- /dev/null
+++ b/pflib-net/effects/implementation/ResistanceEffect.cs
@@ -0,0 +1,17 @@
+namespace pflib_net.effects.implementation;
+
+public readonly struct ResistanceEffect: IEffect
+{
+    public ResistanceEffect(string tag, string reason, int amount)
+    {
+        Tag = tag;
+        Reason = reason;
+        Amount = amount;
+    }
+
+    public string Tag { get; }
+
+    public string Reason { get; }
+
+    public int Amount { get; }
+}
\ No newline at end of file
diff --git a/pflib-net/effects/implementation/TeamEffect.cs b/pflib-net/effects/implementation/TeamEffect.cs
new file mode 100644
index 0000000..71bb1d9
--- /dev/null
+++ b/pflib-net/effects/implementation/TeamEffect.cs
@@ -0,0 +1,13 @@
+namespace pflib_net.effects.implementation;
+
+public readonly struct TeamEffect: IEffect
+{
+    public TeamEffect(int side, string reason)
+    {
+        Side = side;
+        Reason = reason;
+    }
+
+    public int Side { get; }
+    public string Reason { get; }
+}
\ No newline at end of file
diff --git a/pflib-net/effects/implementation/WeaknessEffect.cs b/pflib-net/effects/implementation/WeaknessEffect.cs
new file mode 100644
index 0000000..2dd6756
--- /dev/null
+++ b/pflib-net/effects/implementation/WeaknessEffect.cs
@@ -0,0 +1,16 @@
+namespace pflib_net.effects.implementation;
+
+public readonly struct WeaknessEffect: IEffect
+{
+    public WeaknessEffect(string tag, string reason, int amount)
+    {
+        Tag = tag;
+        Reason = reason;
+        Amount = amount;
+    }
+
+    public string Tag { get; }
+    public string Reason { get; }
+    public int Amount { get; }
+    
+}
\ No newline at end of file