diff --git a/R2API.MonoMod/SurvivorAPI.cs b/R2API.MonoMod/NoInlinePatches.cs
similarity index 57%
rename from R2API.MonoMod/SurvivorAPI.cs
rename to R2API.MonoMod/NoInlinePatches.cs
index dd5b108c..575d3d0b 100644
--- a/R2API.MonoMod/SurvivorAPI.cs
+++ b/R2API.MonoMod/NoInlinePatches.cs
@@ -7,4 +7,9 @@ internal class patch_SurvivorCatalog {
         [MonoModIgnore] [NoInlining]
         public static extern SurvivorDef GetSurvivorDef(SurvivorIndex survivorIndex);
     }
+
+    internal class patch_DifficultyCatalog {
+        [MonoModIgnore] [NoInlining]
+        public static extern DifficultyDef GetDifficultyDef(DifficultyIndex difficultyIndex);
+    }
 }
diff --git a/R2API/DifficultyAPI.cs b/R2API/DifficultyAPI.cs
new file mode 100644
index 00000000..511690ea
--- /dev/null
+++ b/R2API/DifficultyAPI.cs
@@ -0,0 +1,86 @@
+using R2API.Utils;
+using RoR2;
+using System;
+using System.Collections.ObjectModel;
+using UnityEngine;
+
+namespace R2API {
+    [R2APISubmodule]
+    public class DifficultyAPI{
+
+        private static bool difficultyAlreadyAdded = false;
+
+        public static event EventHandler difficultyCatalogReady;
+
+        private const DifficultyIndex VanillaFinalIndex = DifficultyIndex.Hard;//We want to replace this 
+
+        public static ObservableCollection<DifficultyDef> difficultyDefinitions = new ObservableCollection<DifficultyDef>();
+        /// <summary>
+        /// Add a DifficultyDef to the list of available difficulties.
+        /// This must be called before the DifficultyCatalog inits, so before plugin.Start()
+        /// You'll get your new index returned that you can work with for comparing to Run.Instance.selectedDifficulty.
+        /// If this is called after the DifficultyCatalog inits then this will return -1/DifficultyIndex.Invalid and ignore the difficulty
+        /// </summary>
+        /// <param name="difficulty">The difficulty to add.</param>
+        /// <returns>DifficultyIndex.Invalid if it fails. Your index otherwise.</returns>
+        public static DifficultyIndex AddDifficulty(DifficultyDef difficulty) {
+            if (difficultyAlreadyAdded) {
+                R2API.Logger.LogError($"Tried to add difficulty: {difficulty.nameToken} after difficulty list was created");
+                return DifficultyIndex.Invalid;
+            }
+            difficultyDefinitions.Add(difficulty);
+            
+            return VanillaFinalIndex + difficultyDefinitions.Count;
+        }
+
+
+        [R2APISubmoduleInit(Stage = InitStage.SetHooks)]
+        internal static void SetHooks() {
+            difficultyCatalogReady?.Invoke(null, null);
+            On.RoR2.DifficultyCatalog.GetDifficultyDef += GetExtendedDifficultyDef;
+            On.RoR2.RuleDef.FromDifficulty += InitialiseRuleBookAndFinalizeList;
+        }
+
+        [R2APISubmoduleInit(Stage = InitStage.UnsetHooks)]
+        internal static void UnsetHooks() {
+            On.RoR2.DifficultyCatalog.GetDifficultyDef -= GetExtendedDifficultyDef;
+            On.RoR2.RuleDef.FromDifficulty -= InitialiseRuleBookAndFinalizeList;
+        }
+
+        private static DifficultyDef GetExtendedDifficultyDef(On.RoR2.DifficultyCatalog.orig_GetDifficultyDef orig, DifficultyIndex difficultyIndex)
+        {
+            if(difficultyAlreadyAdded)
+                return difficultyDefinitions[(int) difficultyIndex];
+            return orig(difficultyIndex);
+        }
+        private static RuleDef InitialiseRuleBookAndFinalizeList(On.RoR2.RuleDef.orig_FromDifficulty orig)
+        {
+            RuleDef ruleChoices = orig();
+            var vanillaDefs = DifficultyCatalog.difficultyDefs;
+            if (difficultyAlreadyAdded == false) {//Technically this function we are hooking is only called once, but in the weird case it's called multiple times, we don't want to add the definitions again.
+                difficultyAlreadyAdded = true;
+                for (int i = 0; i < vanillaDefs.Length; i++) {
+                    difficultyDefinitions.Insert(i, vanillaDefs[i]);
+                }
+            }
+
+            for ( int i=vanillaDefs.Length; i<difficultyDefinitions.Count;i++){//This basically replicates what the orig does, but that uses the hardcoded enum.Count to end it's loop, instead of the actual array length.
+                DifficultyDef difficultyDef = difficultyDefinitions[i];
+                RuleChoiceDef choice = ruleChoices.AddChoice(Language.GetString(difficultyDef.nameToken), null, false);
+                choice.spritePath = difficultyDef.iconPath;
+                choice.tooltipNameToken = difficultyDef.nameToken;
+                choice.tooltipNameColor = difficultyDef.color;
+                choice.tooltipBodyToken = difficultyDef.descriptionToken;
+                choice.difficultyIndex =  (DifficultyIndex) i;
+            }
+
+            ruleChoices.choices.Sort(delegate(RuleChoiceDef x, RuleChoiceDef y){
+                var xDiffValue = DifficultyCatalog.GetDifficultyDef(x.difficultyIndex).scalingValue;
+                var yDiffValue = DifficultyCatalog.GetDifficultyDef(y.difficultyIndex).scalingValue;
+                return xDiffValue.CompareTo(yDiffValue);            
+            });
+
+            return ruleChoices;
+        }
+    }
+}