diff --git a/CodeWalker.Core/GameFiles/FileTypes/YmapFile.cs b/CodeWalker.Core/GameFiles/FileTypes/YmapFile.cs
index b591209..5c27028 100644
--- a/CodeWalker.Core/GameFiles/FileTypes/YmapFile.cs
+++ b/CodeWalker.Core/GameFiles/FileTypes/YmapFile.cs
@@ -1600,9 +1600,20 @@ namespace CodeWalker.GameFiles
         private void UpdateMloArchetype()
         {
             if (!(MloParent.Archetype is MloArchetype mloArchetype)) return;
-            if (Index >= mloArchetype.entities.Length) return;
 
-            MCEntityDef entity = mloArchetype.entities[Index];
+            MCEntityDef entity = null;
+            if ((MloEntitySet?.Entities != null) && (MloEntitySet?.EntitySet?.Entities != null))
+            {
+                var idx = MloEntitySet.Entities.IndexOf(this);
+                if ((idx < 0) || (idx >= MloEntitySet.EntitySet.Entities.Length)) return;
+                entity = MloEntitySet.EntitySet.Entities[idx];
+            }
+            else
+            {
+                if (Index >= mloArchetype.entities.Length) return;
+                entity = mloArchetype.entities[Index];
+            }
+
             entity._Data.position = _CEntityDef.position;
             entity._Data.rotation = _CEntityDef.rotation;
         }
diff --git a/CodeWalker.Core/GameFiles/MetaTypes/Archetype.cs b/CodeWalker.Core/GameFiles/MetaTypes/Archetype.cs
index 59bfe45..38c2618 100644
--- a/CodeWalker.Core/GameFiles/MetaTypes/Archetype.cs
+++ b/CodeWalker.Core/GameFiles/MetaTypes/Archetype.cs
@@ -169,13 +169,6 @@ namespace CodeWalker.GameFiles
         {
             if (ent == null) return false;
 
-            MloInstanceData mloInstance = ent.MloParent?.MloInstance;
-            MCEntityDef ymcent = mloInstance?.TryGetArchetypeEntity(ent);
-            if (ymcent != null)
-            {
-                return true;//this entity already exists in this MLO...
-            }
-
             if (roomIndex >= (rooms?.Length ?? 0))
             {
                 throw new ArgumentOutOfRangeException($"Room index {roomIndex} exceeds the amount of rooms in {Name}.");
@@ -194,11 +187,9 @@ namespace CodeWalker.GameFiles
 
             if ((roomIndex >= 0) || (portalIndex >= 0))
             {
-                if (entities == null) entities = new MCEntityDef[0];
-
-                List<MCEntityDef> entList = entities.ToList();
+                var entList = entities?.ToList() ?? new List<MCEntityDef>();
+                ent.Index = entList.Count;
                 entList.Add(mcEntityDef);
-                ent.Index = entList.IndexOf(mcEntityDef);
                 entities = entList.ToArray();
 
                 if (roomIndex >= 0)
@@ -217,34 +208,60 @@ namespace CodeWalker.GameFiles
             else if (entsetIndex >= 0)
             {
                 var entset = entitySets[entsetIndex];
-                
-                //// in the case of entity sets, adding to the entity set instance adds to the base set.... so don't need to add it here..
-                //entset.AddEntity(mcEntityDef);
 
-                MloInstanceEntitySet entseti = null;
-                mloInstance?.EntitySets.TryGetValue(entset._Data.name, out entseti);
-                ent.MloEntitySet = entseti;
+                var entList = entset.Entities?.ToList() ?? new List<MCEntityDef>();
+                entList.Add(mcEntityDef);
+                entset.Entities = entList.ToArray();
+
+                var locs = entset.Locations?.ToList() ?? new List<uint>();
+                locs.Add(0);//choose a better default location?
+                entset.Locations = locs.ToArray();
+
+
+                var mloInstance = ent.MloParent?.MloInstance;
+                if ((mloInstance?.EntitySets != null) && (entsetIndex < mloInstance.EntitySets.Length))
+                {
+                    ent.MloEntitySet = mloInstance.EntitySets[entsetIndex];
+                }
             }
             else return false;
 
+            UpdateAllEntityIndexes();
 
             return true;
         }
-
-
-
         public bool RemoveEntity(YmapEntityDef ent)
         {
+            if (ent == null) return false;
+
+            if ((ent.MloEntitySet?.Entities != null) && (ent.MloEntitySet?.EntitySet != null))
+            {
+                var instents = ent.MloEntitySet.Entities;
+                var set = ent.MloEntitySet.EntitySet;
+                var idx = instents.IndexOf(ent);
+                if (idx >= 0)
+                {
+                    var ents = set.Entities.ToList();
+                    ents.RemoveAt(idx);
+                    set.Entities = ents.ToArray();
+
+                    var locs = set.Locations.ToList();
+                    locs.RemoveAt(idx);
+                    set.Locations = locs.ToArray();
+
+                    UpdateAllEntityIndexes();
+                    return true;
+                }
+                return false;
+            }
+
             if (ent.Index >= entities.Length) return false;
 
-            MCEntityDef delent = entities[ent.Index];
-            MloInstanceData inst = ent.MloParent?.MloInstance;
-            if (inst == null) return false;
-
+            var delent = entities[ent.Index];
             if (delent != null)
             {
-                MCEntityDef[] newentities = new MCEntityDef[entities.Length - 1];
-                bool didDel = false;
+                var newentities = new MCEntityDef[entities.Length - 1];
+                var didDel = false;
                 int index = 0;
                 int delIndex = 0;
                 for (int i = 0; i < entities.Length; i++)
@@ -256,9 +273,8 @@ namespace CodeWalker.GameFiles
                         continue;
                     }
 
-                    newentities[index] = entities[i];
-                    YmapEntityDef ymapEntityDef = inst.TryGetYmapEntity(newentities[index]);
-                    if (ymapEntityDef != null) ymapEntityDef.Index = index;
+                    var newent = entities[i];
+                    newentities[index] = newent;
                     index++;
                 }
 
@@ -268,6 +284,7 @@ namespace CodeWalker.GameFiles
                 {
                     FixRoomIndexes(delIndex);
                     FixPortalIndexes(delIndex);
+                    UpdateAllEntityIndexes();
                 }
                 return didDel;
             }
@@ -275,7 +292,6 @@ namespace CodeWalker.GameFiles
             return false;
         }
 
-
         public void AddRoom(MCMloRoomDef room)
         {
             if (room == null) return;
@@ -294,6 +310,11 @@ namespace CodeWalker.GameFiles
             var newrooms = rooms.ToList();
             newrooms.Remove(room);
             rooms = newrooms.ToArray();
+
+            for (int i = 0; i < rooms.Length; i++)
+            {
+                rooms[i].Index = i;
+            }
         }
 
         public void AddPortal(MCMloPortalDef portal)
@@ -314,6 +335,11 @@ namespace CodeWalker.GameFiles
             var newportals = portals.ToList();
             newportals.Remove(portal);
             portals = newportals.ToArray();
+
+            for (int i = 0; i < portals.Length; i++)
+            {
+                portals[i].Index = i;
+            }
         }
 
         public void AddEntitySet(MCMloEntitySet set)
@@ -334,6 +360,13 @@ namespace CodeWalker.GameFiles
             var newsets = entitySets.ToList();
             newsets.Remove(set);
             entitySets = newsets.ToArray();
+
+            for (int i = 0; i < entitySets.Length; i++)
+            {
+                entitySets[i].Index = i;
+            }
+
+            UpdateAllEntityIndexes();
         }
 
 
@@ -357,7 +390,6 @@ namespace CodeWalker.GameFiles
                 portal.AttachedObjects = newAttachedObjects.ToArray();
             }
         }
-
         private void FixRoomIndexes(int deletedIndex)
         {
             foreach (var room in rooms)
@@ -376,6 +408,30 @@ namespace CodeWalker.GameFiles
             }
         }
 
+        private void UpdateAllEntityIndexes()
+        {
+            var index = 0;
+            if (entities != null)
+            {
+                for (int i = 0; i < entities.Length; i++)
+                {
+                    entities[i].Index = index++;
+                }
+            }
+            if (entitySets != null)
+            {
+                for (int e = 0; e < entitySets.Length; e++)
+                {
+                    var set = entitySets[e];
+                    if (set?.Entities == null) continue;
+                    for (int i = 0; i < set.Entities.Length; i++)
+                    {
+                        set.Entities[i].Index = index++;
+                    }
+                }
+            }
+        }
+
         public void LoadChildren(Meta meta)
         {
             var centities = MetaTypes.ConvertDataArray<CEntityDef>(meta, MetaName.CEntityDef, _MloArchetypeDefData.entities);
@@ -416,6 +472,7 @@ namespace CodeWalker.GameFiles
                 {
                     entitySets[i] = new MCMloEntitySet(meta, centitySets[i], this) { OwnerMlo = this, Index = i };
                 }
+                UpdateAllEntityIndexes();
             }
 
 
@@ -520,13 +577,12 @@ namespace CodeWalker.GameFiles
         public uint[] defaultEntitySets { get; set; }
 
         public YmapEntityDef[] Entities { get; set; }
-        public Dictionary<MetaHash, MloInstanceEntitySet> EntitySets { get; set; }
+        public MloInstanceEntitySet[] EntitySets { get; set; }
 
         public MloInstanceData(YmapEntityDef owner, MloArchetype mloa)
         {
             Owner = owner;
             MloArch = mloa;
-            EntitySets = new Dictionary<MetaHash, MloInstanceEntitySet>();
         }
 
         public void CreateYmapEntities()
@@ -538,7 +594,7 @@ namespace CodeWalker.GameFiles
             var entlist = new List<YmapEntityDef>();
             for (int i = 0; i < ec; i++)
             {
-                YmapEntityDef e = CreateYmapEntity(Owner, MloArch.entities[i], i);
+                var e = CreateYmapEntity(Owner, MloArch.entities[i], i);
                 entlist.Add(e);
             }
 
@@ -547,32 +603,32 @@ namespace CodeWalker.GameFiles
             var entitySets = MloArch.entitySets;
             if (entitySets != null)
             {
+                EntitySets = new MloInstanceEntitySet[entitySets.Length];
                 for (int i = 0; i < entitySets.Length; i++)
                 {
                     var entitySet = entitySets[i];
+                    var instset = new MloInstanceEntitySet(entitySet, this);
                     if (entitySet.Entities != null)
                     {
-                        EntitySets[entitySet._Data.name] = new MloInstanceEntitySet(entitySet, this);
-                        MloInstanceEntitySet instset = EntitySets[entitySet._Data.name];
                         for (int j = 0; j < entitySet.Entities.Length; j++)
                         {
-                            YmapEntityDef e = CreateYmapEntity(Owner, entitySet.Entities[j], lasti);
-                            EntitySets[entitySet._Data.name].Entities.Add(e);
+                            var e = CreateYmapEntity(Owner, entitySet.Entities[j], lasti);
+                            instset.Entities.Add(e);
                             e.MloEntitySet = instset;
                             lasti++;
                         }
                     }
+                    EntitySets[i] = instset;
                 }
             }
 
-            if ((defaultEntitySets != null) && (entitySets != null))
+            if ((defaultEntitySets != null) && (EntitySets != null))
             {
                 for (var i = 0; i < defaultEntitySets.Length; i++)
                 {
                     uint index = defaultEntitySets[i];
-                    if (index >= entitySets.Length) continue;
-                    MCMloEntitySet set = entitySets[index];
-                    MloInstanceEntitySet instset = EntitySets[set._Data.name];
+                    if (index >= EntitySets.Length) continue;
+                    var instset = EntitySets[index];
                     instset.Visible = true;
                 }
             }
@@ -602,9 +658,10 @@ namespace CodeWalker.GameFiles
 
             if (EntitySets != null)
             {
-                foreach (var entitySet in EntitySets)
+                for (int e = 0; e < EntitySets.Length; e++)
                 {
-                    var entities = entitySet.Value.Entities;
+                    var entitySet = EntitySets[e];
+                    var entities = entitySet.Entities;
                     if (entities == null) continue;
 
                     for (int i = 0; i < entities.Count; i++)
@@ -699,26 +756,31 @@ namespace CodeWalker.GameFiles
             if (ymapEntity == null) return null;
             if (Owner?.Archetype == null) return null;
             if (!(Owner.Archetype is MloArchetype mloa)) return null;
-            if (ymapEntity.Index < mloa.entities.Length)
+
+            var index = Array.FindIndex(Entities, x => x == ymapEntity);
+            if ((index >= 0) && (index < mloa.entities.Length))
             {
-                return mloa.entities[ymapEntity.Index];
+                return mloa.entities[index];
             }
-            else
+
+            if (EntitySets != null)
             {
-                var idx = ymapEntity.Index - mloa.entities.Length;
-                if (mloa.entitySets == null) return null;
-                for (int i = 0; i < mloa.entitySets.Length; i++)
+                for (int e = 0; e < EntitySets.Length; e++)
                 {
-                    var set = mloa.entitySets[i];
-                    if (set?.Entities == null) continue;
-                    if (idx < set.Entities.Length)
+                    var entset = EntitySets[e];
+                    var ents = entset.Entities;
+                    var set = entset.EntitySet;
+                    var setents = set?.Entities;
+                    if ((ents == null) || (setents == null)) continue;
+                    var idx = ents.IndexOf(ymapEntity);
+                    if ((idx >= 0) && (idx < setents.Length))
                     {
-                        return set.Entities[idx];
+                        return setents[idx];
                     }
-                    idx -= set.Entities.Length;
                 }
-                return null;
             }
+
+            return null;
         }
 
         public YmapEntityDef TryGetYmapEntity(MCEntityDef mcEntity)
@@ -733,17 +795,20 @@ namespace CodeWalker.GameFiles
                 return Entities[index];
             }
 
-            foreach (var entset in EntitySets.Values)
+            if (EntitySets != null)
             {
-                var ents = entset.Entities;
-                var set = entset.EntitySet;
-                var setents = set?.Entities;
-                if ((ents == null) || (setents == null)) continue;
-
-                var idx = Array.FindIndex(setents, x => x == mcEntity);
-                if ((idx >= 0) && (idx < ents.Count))
+                for (int e = 0; e < EntitySets.Length; e++)
                 {
-                    return ents[idx];
+                    var entset = EntitySets[e];
+                    var ents = entset.Entities;
+                    var set = entset.EntitySet;
+                    var setents = set?.Entities;
+                    if ((ents == null) || (setents == null)) continue;
+                    var idx = Array.FindIndex(setents, x => x == mcEntity);
+                    if ((idx >= 0) && (idx < ents.Count))
+                    {
+                        return ents[idx];
+                    }
                 }
             }
 
@@ -771,8 +836,24 @@ namespace CodeWalker.GameFiles
 
             for (int i = 0; i < Entities.Length; i++)
             {
-                YmapEntityDef e = Entities[i];
-                UpdateEntity(e);
+                var ent = Entities[i];
+                UpdateEntity(ent);
+            }
+
+            if (EntitySets != null)
+            {
+                for (int e = 0; e < EntitySets.Length; e++)
+                {
+                    var entset = EntitySets[e];
+                    if (entset?.Entities != null)
+                    {
+                        for (int i = 0; i < entset.Entities.Count; i++)
+                        {
+                            var ent = entset.Entities[i];
+                            UpdateEntity(ent);
+                        }
+                    }
+                }
             }
 
         }
@@ -792,23 +873,27 @@ namespace CodeWalker.GameFiles
             if (e.MloEntitySet != null)
             {
                 e.MloEntitySet.AddEntity(e);
-                return;
             }
-
-            if (Entities == null) Entities = new YmapEntityDef[0];
-            var entities = Entities.ToList();
-            entities.Add(e);
-            Entities = entities.ToArray();
+            else
+            {
+                if (Entities == null) Entities = new YmapEntityDef[0];
+                var entities = Entities.ToList();
+                entities.Add(e);
+                Entities = entities.ToArray();
+            }
+            UpdateAllEntityIndexes();
         }
 
         public bool DeleteEntity(YmapEntityDef ent)
         {
+            var del = false;
             if (ent.MloEntitySet != null)
             {
-                return ent.MloEntitySet.DeleteEntity(ent);
+                del = ent.MloEntitySet.DeleteEntity(ent);
+                UpdateAllEntityIndexes();
+                return del;
             }
 
-
             if (Entities == null)
             {
                 throw new NullReferenceException("The Entities list returned null in our MloInstanceData. This could be an issue with initialization. The MloInstance probably doesn't exist.");
@@ -819,13 +904,11 @@ namespace CodeWalker.GameFiles
             }
 
             int index = 0;
-            YmapEntityDef[] newentities = new YmapEntityDef[Entities.Length - 1];
-            YmapEntityDef delentity = Entities[ent.Index];
-            bool del = false;
+            var newentities = new YmapEntityDef[Entities.Length - 1];
 
             for (int i = 0; i < Entities.Length; i++)
             {
-                if (Entities[i] == delentity)
+                if (i == ent.Index)
                 {
                     del = true;
                     continue;
@@ -836,36 +919,43 @@ namespace CodeWalker.GameFiles
             }
             if (del)
             {
-                if (Owner.Archetype is MloArchetype arch)
-                {
-                    if (arch.RemoveEntity(ent))
-                    {
-                        // Delete was successful...
-                        Entities = newentities;
-                        return true;
-                    }
-                    else throw new ArgumentException("The entity could not be removed from the MloArchetype! This shouldn't happen...");
-                }
-                else throw new InvalidCastException("The owner of this archetype's archetype definition is not an MloArchetype. (wtf?)");
+                Entities = newentities;
+                UpdateAllEntityIndexes();
+                return true;
             }
             else throw new ArgumentException("The entity specified was not found in this MloInstance. It cannot be deleted.");
         }
 
+        public void AddEntitySet(MCMloEntitySet set)
+        {
+            var instset = new MloInstanceEntitySet(set, this);
+            var esets = EntitySets?.ToList() ?? new List<MloInstanceEntitySet>();
+            esets.Add(instset);
+            EntitySets = esets.ToArray();
+        }
+
+        public bool DeleteEntitySet(MCMloEntitySet set)
+        {
+            if (EntitySets == null) return false;
+            var esets = EntitySets.ToList();
+            var rem = esets.RemoveAll(s => s.EntitySet == set);
+            EntitySets = esets.ToArray();
+            UpdateAllEntityIndexes();
+            return rem == 1;
+        }
+
         public void UpdateDefaultEntitySets()
         {
             var list = new List<uint>();
-            var mloarch = Owner?.Archetype as MloArchetype;
 
-            if (mloarch?.entitySets != null)
+            if (EntitySets != null)
             {
-                for (uint i = 0; i < mloarch.entitySets.Length; i++)
+                for (uint i = 0; i < EntitySets.Length; i++)
                 {
-                    var entset = mloarch.entitySets[i];
-                    MloInstanceEntitySet instset = null;
-                    EntitySets.TryGetValue(entset._Data.name, out instset);
-                    if (instset != null)
+                    var entset = EntitySets[i];
+                    if (entset != null)
                     {
-                        if (instset.Visible)
+                        if (entset.Visible)
                         {
                             list.Add(i);
                         }
@@ -875,6 +965,30 @@ namespace CodeWalker.GameFiles
 
             defaultEntitySets = list.ToArray();
         }
+
+        private void UpdateAllEntityIndexes()
+        {
+            var index = 0;
+            if (Entities != null)
+            {
+                for (int i = 0; i < Entities.Length; i++)
+                {
+                    Entities[i].Index = index++;
+                }
+            }
+            if (EntitySets != null)
+            {
+                for (int e = 0; e < EntitySets.Length; e++)
+                {
+                    var set = EntitySets[e];
+                    if (set?.Entities == null) continue;
+                    for (int i = 0; i < set.Entities.Count; i++)
+                    {
+                        set.Entities[i].Index = index++;
+                    }
+                }
+            }
+        }
     }
 
     [TypeConverter(typeof(ExpandableObjectConverter))]
@@ -911,54 +1025,12 @@ namespace CodeWalker.GameFiles
         public void AddEntity(YmapEntityDef ent)
         {
             if (Entities == null) Entities = new List<YmapEntityDef>();
-            ent.Index = Entities.Count;
             Entities.Add(ent);
-            if (EntitySet != null)
-            {
-                var ents = EntitySet.Entities.ToList();
-                var ment = new MCEntityDef(ref ent._CEntityDef, Instance?.MloArch);
-                ents.Add(ment);
-                EntitySet.Entities = ents.ToArray();
-            }
-            var locs = Locations?.ToList() ?? new List<uint>();
-            locs.Add(0);//choose a better default location?
-            Locations = locs.ToArray();
         }
         public bool DeleteEntity(YmapEntityDef ent)
         {
-            var locs = Locations;
-            if ((Entities == null) || (locs == null)) return false;
-
-            var idx = Entities.IndexOf(ent);
-            if ((idx < 0) || (idx >= locs.Length)) return false;
-
-            var newlocs = new uint[locs.Length-1];
-            var j = 0;
-            for (int i = 0; i < locs.Length; i++)
-            {
-                if (i == idx) continue;
-                newlocs[j] = locs[i];
-                j++;
-            }
-            Locations = newlocs;
-
-            var i0 = (Entities.Count > 0) ? Entities[0].Index : 0;
-
-            Entities.RemoveAt(idx);
-
-            for (int i = 0; i < Entities.Count; i++)
-            {
-                Entities[i].Index = i0 + i;
-            }
-
-            if (EntitySet?.Entities != null)
-            {
-                var ents = EntitySet.Entities.ToList();
-                ents.RemoveAt(idx);
-                EntitySet.Entities = ents.ToArray();
-            }
-
-            return true;
+            if (Entities == null) return false;
+            return Entities.Remove(ent);
         }
     }
 
diff --git a/CodeWalker.Core/GameFiles/MetaTypes/MetaTypes.cs b/CodeWalker.Core/GameFiles/MetaTypes/MetaTypes.cs
index d95cc7d..830585e 100644
--- a/CodeWalker.Core/GameFiles/MetaTypes/MetaTypes.cs
+++ b/CodeWalker.Core/GameFiles/MetaTypes/MetaTypes.cs
@@ -2604,7 +2604,7 @@ namespace CodeWalker.GameFiles
         {
             get
             {
-                return _Data.roomFrom.ToString() + " to " + _Data.roomTo.ToString();
+                return Index.ToString() + ": " + _Data.roomFrom.ToString() + " to " + _Data.roomTo.ToString();
             }
         }
 
diff --git a/CodeWalker.Core/World/Space.cs b/CodeWalker.Core/World/Space.cs
index 46f88ea..8dcafb2 100644
--- a/CodeWalker.Core/World/Space.cs
+++ b/CodeWalker.Core/World/Space.cs
@@ -1286,11 +1286,12 @@ namespace CodeWalker.World
             }
             if (mlodat.EntitySets != null)
             {
-                foreach (var entitysets in mlodat.EntitySets)
+                for (int e = 0; e < mlodat.EntitySets.Length; e++)
                 {
-                    var entityset = entitysets.Value;
+                    var entityset = mlodat.EntitySets[e];
                     if (!entityset.Visible) continue;
                     var entities = entityset.Entities;
+                    if (entities == null) continue;
                     for (int i = 0; i < entities.Count; i++) //should really improve this by using rooms!
                     {
                         var intent = entities[i];
@@ -1509,11 +1510,12 @@ namespace CodeWalker.World
             }
             if (mlodat.EntitySets != null)
             {
-                foreach (var entitysets in mlodat.EntitySets)
+                for (int e = 0; e < mlodat.EntitySets.Length; e++)
                 {
-                    var entityset = entitysets.Value;
+                    var entityset = mlodat.EntitySets[e];
                     if (!entityset.Visible) continue;
                     var entities = entityset.Entities;
+                    if (entities == null) continue;
                     for (int i = 0; i < entities.Count; i++) //should really improve this by using rooms!
                     {
                         var intent = entities[i];
diff --git a/Project/Panels/EditYmapEntityPanel.cs b/Project/Panels/EditYmapEntityPanel.cs
index bd1f447..80c0eb5 100644
--- a/Project/Panels/EditYmapEntityPanel.cs
+++ b/Project/Panels/EditYmapEntityPanel.cs
@@ -130,10 +130,15 @@ namespace CodeWalker.Project.Panels
                     MiloFloorIDTextBox.Text = milo.floorId.ToString();
                     MiloNumExitPortalsTextBox.Text = milo.numExitPortals.ToString();
                     MiloFlagsTextBox.Text = milo.MLOInstflags.ToString();
-                    foreach (var sets in CurrentEntity.MloInstance.EntitySets)
+                    if (CurrentEntity.MloInstance.EntitySets != null)
                     {
-                        MloInstanceEntitySet set = sets.Value;
-                        MiloEntitySetsListBox.Items.Add(set.EntitySet.ToString(), set.Visible);
+                        foreach (var set in CurrentEntity.MloInstance.EntitySets)
+                        {
+                            if (set?.EntitySet != null)
+                            {
+                                MiloEntitySetsListBox.Items.Add(set.EntitySet.ToString(), set.Visible);
+                            }
+                        }
                     }
                 }
                 else
@@ -793,11 +798,9 @@ namespace CodeWalker.Project.Panels
         {
             if (populatingui) return;
             var inst = CurrentEntity?.MloInstance;
-            var mloarch = CurrentEntity?.Archetype as MloArchetype;
-            if ((inst != null) && (mloarch != null))
+            if ((inst != null) && (inst.EntitySets != null) && (e.Index < inst.EntitySets.Length) && (e.Index >= 0))
             {
-                MloInstanceEntitySet mloInstanceEntitySet = inst.EntitySets[mloarch.entitySets[e.Index]._Data.name];
-                mloInstanceEntitySet.Visible = e.NewValue == CheckState.Checked;
+                inst.EntitySets[e.Index].Visible = e.NewValue == CheckState.Checked;
                 return;
             }
             e.NewValue = CheckState.Unchecked;
diff --git a/Project/Panels/EditYtypMloRoomPanel.cs b/Project/Panels/EditYtypMloRoomPanel.cs
index f556510..11dd9b6 100644
--- a/Project/Panels/EditYtypMloRoomPanel.cs
+++ b/Project/Panels/EditYtypMloRoomPanel.cs
@@ -82,7 +82,7 @@ namespace CodeWalker.Project.Panels
                 TreeNode tn = ProjectForm.ProjectExplorer?.FindMloRoomTreeNode(CurrentRoom);
                 if (tn != null)
                 {
-                    tn.Text = CurrentRoom.RoomName;
+                    tn.Text = CurrentRoom.Index.ToString() + ": " + CurrentRoom.RoomName;
                 }
 
                 UpdateFormTitle();
diff --git a/Project/Panels/ProjectExplorerPanel.cs b/Project/Panels/ProjectExplorerPanel.cs
index f963f64..614874f 100644
--- a/Project/Panels/ProjectExplorerPanel.cs
+++ b/Project/Panels/ProjectExplorerPanel.cs
@@ -281,7 +281,7 @@ namespace CodeWalker.Project.Panels
                             for (int j = 0; j < rooms.Length; j++)
                             {
                                 var room = rooms[j];
-                                var roomnode = roomsnode.Nodes.Add(room.RoomName);
+                                var roomnode = roomsnode.Nodes.Add(room.Index.ToString() + ": " + room.RoomName);
                                 roomnode.Tag = room;
                                 var roomentities = room.AttachedObjects;
                                 if ((roomentities != null) && (entities != null))
@@ -646,6 +646,10 @@ namespace CodeWalker.Project.Panels
         }
         public void SetYmapHasChanged(YmapFile ymap, bool changed)
         {
+            if (ymap != null)
+            {
+                ymap.HasChanged = true;
+            }
             if (ProjectTreeView.Nodes.Count > 0)
             {
                 var pnode = ProjectTreeView.Nodes[0];
@@ -670,6 +674,10 @@ namespace CodeWalker.Project.Panels
         }
         public void SetYtypHasChanged(YtypFile ytyp, bool changed)
         {
+            if (ytyp != null)
+            {
+                ytyp.HasChanged = true;
+            }
             if (ProjectTreeView.Nodes.Count > 0)
             {
                 var pnode = ProjectTreeView.Nodes[0];
@@ -694,6 +702,10 @@ namespace CodeWalker.Project.Panels
         }
         public void SetYndHasChanged(YndFile ynd, bool changed)
         {
+            if (ynd != null)
+            {
+                ynd.HasChanged = true;
+            }
             if (ProjectTreeView.Nodes.Count > 0)
             {
                 var pnode = ProjectTreeView.Nodes[0];
@@ -718,6 +730,10 @@ namespace CodeWalker.Project.Panels
         }
         public void SetYnvHasChanged(YnvFile ynv, bool changed)
         {
+            if (ynv != null)
+            {
+                ynv.HasChanged = true;
+            }
             if (ProjectTreeView.Nodes.Count > 0)
             {
                 var pnode = ProjectTreeView.Nodes[0];
@@ -742,6 +758,10 @@ namespace CodeWalker.Project.Panels
         }
         public void SetTrainTrackHasChanged(TrainTrack track, bool changed)
         {
+            if (track != null)
+            {
+                track.HasChanged = true;
+            }
             if (ProjectTreeView.Nodes.Count > 0)
             {
                 var pnode = ProjectTreeView.Nodes[0];
@@ -766,6 +786,10 @@ namespace CodeWalker.Project.Panels
         }
         public void SetScenarioHasChanged(YmtFile scenario, bool changed)
         {
+            if (scenario != null)
+            {
+                scenario.HasChanged = true;
+            }
             if (ProjectTreeView.Nodes.Count > 0)
             {
                 var pnode = ProjectTreeView.Nodes[0];
@@ -790,6 +814,10 @@ namespace CodeWalker.Project.Panels
         }
         public void SetAudioRelHasChanged(RelFile rel, bool changed)
         {
+            if (rel != null)
+            {
+                rel.HasChanged = true;
+            }
             if (ProjectTreeView.Nodes.Count > 0)
             {
                 var pnode = ProjectTreeView.Nodes[0];
@@ -814,6 +842,10 @@ namespace CodeWalker.Project.Panels
         }
         public void SetGrassBatchHasChanged(YmapGrassInstanceBatch batch, bool changed)
         {
+            if (batch?.Ymap != null)
+            {
+                batch.Ymap.HasChanged = true;
+            }
             if (ProjectTreeView.Nodes.Count > 0)
             {
                 var gbnode = FindGrassTreeNode(batch);
@@ -1791,6 +1823,33 @@ namespace CodeWalker.Project.Panels
                 tn.Parent.Nodes.Remove(tn);
             }
         }
+        public void RemoveMloRoomTreeNode(MCMloRoomDef room)
+        {
+            var tn = FindMloRoomTreeNode(room);
+            if ((tn != null) && (tn.Parent != null))
+            {
+                tn.Parent.Text = "Rooms (" + (room.OwnerMlo?.rooms?.Length.ToString() ?? "0") + ")";
+                tn.Parent.Nodes.Remove(tn);
+            }
+        }
+        public void RemoveMloPortalTreeNode(MCMloPortalDef portal)
+        {
+            var tn = FindMloPortalTreeNode(portal);
+            if ((tn != null) && (tn.Parent != null))
+            {
+                tn.Parent.Text = "Portals (" + (portal.OwnerMlo?.portals?.Length.ToString() ?? "0") + ")";
+                tn.Parent.Nodes.Remove(tn);
+            }
+        }
+        public void RemoveMloEntitySetTreeNode(MCMloEntitySet set)
+        {
+            var tn = FindMloEntitySetTreeNode(set);
+            if ((tn != null) && (tn.Parent != null))
+            {
+                tn.Parent.Text = "Entity Sets (" + (set.OwnerMlo?.entitySets?.Length.ToString() ?? "0") + ")";
+                tn.Parent.Nodes.Remove(tn);
+            }
+        }
         public void RemovePathNodeTreeNode(YndNode node)
         {
             var tn = FindPathNodeTreeNode(node);
diff --git a/Project/ProjectForm.cs b/Project/ProjectForm.cs
index 6f5e017..b9f02cf 100644
--- a/Project/ProjectForm.cs
+++ b/Project/ProjectForm.cs
@@ -706,7 +706,6 @@ namespace CodeWalker.Project
                 if (instance != null)
                 {
                     CurrentEntity = instance.TryGetYmapEntity(CurrentMloEntity);
-
                     CurrentYmapFile = instance.Owner?.Ymap;
                 }
 
@@ -721,7 +720,6 @@ namespace CodeWalker.Project
                 else
                 {
                     CurrentArchetype = CurrentEntity.Archetype;
-
                     CurrentYmapFile = CurrentEntity.Ymap;
                 }
             }
@@ -2339,45 +2337,50 @@ namespace CodeWalker.Project
                 return;
             }
 
+            if ((CurrentMloEntity == null) && (CurrentEntity != null))
+            {
+                CurrentMloEntity = mloInstance.TryGetArchetypeEntity(CurrentEntity);
+            }
+
             if ((CurrentMloRoom == null) && (CurrentMloPortal == null) && (CurrentMloEntitySet == null))
             {
-                if ((mloArch.rooms?.Length??0) <= 0)
+                if (CurrentMloEntity != null)
                 {
-                    MessageBox.Show($@"Mlo {mloArch.Name} has no rooms! Cannot create entity.");
-                    return;
+                    CurrentMloRoom = mloArch.GetEntityRoom(CurrentMloEntity);
+                    CurrentMloPortal = mloArch.GetEntityPortal(CurrentMloEntity);
+                    CurrentMloEntitySet = mloArch.GetEntitySet(CurrentMloEntity);
+                }
+                else
+                {
+                    if ((mloArch.rooms?.Length??0) <= 0)
+                    {
+                        MessageBox.Show($@"Mlo {mloArch.Name} has no rooms! Cannot create entity.");
+                        return;
+                    }
+                    CurrentMloRoom = mloArch.rooms[0];
                 }
-                CurrentMloRoom = mloArch?.GetEntityRoom(CurrentMloEntity);
             }
 
 
             int roomIndex = CurrentMloRoom?.Index ?? -1;
-            if (roomIndex >= 0)
+            if (roomIndex >= (mloArch.rooms?.Length ?? 0))
             {
-                if (roomIndex >= (mloArch.rooms?.Length??0))
-                {
-                    MessageBox.Show($@"Room at index {roomIndex} does not exist in {mloArch.Name}! {mloArch.Name} only has {(mloArch.rooms?.Length??0)} rooms.");
-                    return;
-                }
+                MessageBox.Show($@"Room at index {roomIndex} does not exist in {mloArch.Name}! {mloArch.Name} only has {(mloArch.rooms?.Length ?? 0)} rooms.");
+                return;
             }
 
             int portalIndex = CurrentMloPortal?.Index ?? -1;
-            if (portalIndex >= 0)
+            if (portalIndex >= (mloArch.portals?.Length ?? 0))
             {
-                if (portalIndex >= (mloArch.portals?.Length??0))
-                {
-                    MessageBox.Show($@"Portal at index {portalIndex} does not exist in {mloArch.Name}! {mloArch.Name} only has {(mloArch.portals?.Length??0)} portals.");
-                    return;
-                }
+                MessageBox.Show($@"Portal at index {portalIndex} does not exist in {mloArch.Name}! {mloArch.Name} only has {(mloArch.portals?.Length ?? 0)} portals.");
+                return;
             }
 
             int entsetIndex = CurrentMloEntitySet?.Index ?? -1;
-            if (entsetIndex >= 0)
+            if (entsetIndex >= (mloArch.entitySets?.Length ?? 0))
             {
-                if (entsetIndex >= (mloArch.entitySets?.Length ?? 0))
-                {
-                    MessageBox.Show($@"EntitySet at index {entsetIndex} does not exist in {mloArch.Name}! {mloArch.Name} only has {(mloArch.entitySets?.Length ?? 0)} entitySets.");
-                    return;
-                }
+                MessageBox.Show($@"EntitySet at index {entsetIndex} does not exist in {mloArch.Name}! {mloArch.Name} only has {(mloArch.entitySets?.Length ?? 0)} entitySets.");
+                return;
             }
 
 
@@ -2418,8 +2421,8 @@ namespace CodeWalker.Project
             cent.rotation = rot.ToVector4();
 
             var createindex = mloArch.entities.Length;
-            MCEntityDef ment = new MCEntityDef(ref cent, mloArch);
-            YmapEntityDef outEnt = mloInstance.CreateYmapEntity(mloInstance.Owner, ment, createindex);
+            var ment = new MCEntityDef(ref cent, mloArch);
+            var outEnt = mloInstance.CreateYmapEntity(mloInstance.Owner, ment, createindex);
 
             try
             {
@@ -2428,14 +2431,14 @@ namespace CodeWalker.Project
                     lock (WorldForm.RenderSyncRoot) //don't try to do this while rendering...
                     {
                         mloArch.AddEntity(outEnt, roomIndex, portalIndex, entsetIndex);
-                        mloInstance.AddEntity(outEnt);//in the case of entitySets, this will add to the archetype entity set... weird and bad - should change this!
+                        mloInstance.AddEntity(outEnt);
                         outEnt.SetArchetype(GameFileCache.GetArchetype(cent.archetypeName));
                     }
                 }
                 else
                 {
                     mloArch.AddEntity(outEnt, roomIndex, portalIndex, entsetIndex);
-                    mloInstance.AddEntity(outEnt);//in the case of entitySets, this will add to the archetype entity set... weird and bad - should change this!
+                    mloInstance.AddEntity(outEnt);
                     outEnt.SetArchetype(GameFileCache.GetArchetype(cent.archetypeName));
                 }
             }
@@ -2445,14 +2448,17 @@ namespace CodeWalker.Project
                 return;
             }
 
+            ment = mloInstance.TryGetArchetypeEntity(outEnt);
+
             LoadProjectTree();
-            ProjectExplorer?.TrySelectMloEntityTreeNode(mloInstance.TryGetArchetypeEntity(outEnt));
+            ProjectExplorer?.TrySelectMloEntityTreeNode(ment);
             CurrentEntity = outEnt;
+            CurrentMloEntity = ment;
             CurrentYtypFile = CurrentEntity.MloParent?.Archetype?.Ytyp;
         }
         public void NewMloRoom(MCMloRoomDef copy = null)
         {
-            var mlo = CurrentMloRoom?.OwnerMlo ?? CurrentMloPortal?.OwnerMlo ?? CurrentMloEntitySet?.OwnerMlo ?? (CurrentEntity?.MloParent.Archetype as MloArchetype);
+            var mlo = CurrentMloRoom?.OwnerMlo ?? CurrentMloPortal?.OwnerMlo ?? CurrentMloEntitySet?.OwnerMlo ?? (CurrentEntity?.MloParent.Archetype as MloArchetype) ?? (CurrentArchetype as MloArchetype);
             if (mlo == null) return;
 
             if (copy == null)
@@ -2488,7 +2494,7 @@ namespace CodeWalker.Project
         }
         public void NewMloPortal(MCMloPortalDef copy = null)
         {
-            var mlo = CurrentMloRoom?.OwnerMlo ?? CurrentMloPortal?.OwnerMlo ?? CurrentMloEntitySet?.OwnerMlo ?? (CurrentEntity?.MloParent.Archetype as MloArchetype);
+            var mlo = CurrentMloRoom?.OwnerMlo ?? CurrentMloPortal?.OwnerMlo ?? CurrentMloEntitySet?.OwnerMlo ?? (CurrentEntity?.MloParent.Archetype as MloArchetype) ?? (CurrentArchetype as MloArchetype);
             if (mlo == null) return;
 
             if (copy == null)
@@ -2500,13 +2506,17 @@ namespace CodeWalker.Project
             if (copy != null)
             {
                 portal._Data = copy._Data;
-                portal.Corners = (Vector4[])copy.Corners.Clone();
+                portal.Corners = (Vector4[])copy.Corners?.Clone();
             }
             else
             {
                 portal._Data.roomFrom = 1;
                 portal._Data.roomTo = 0;
             }
+            if (portal.Corners == null)
+            {
+                portal.Corners = new[] { new Vector4(0, 0, 0, float.NaN), new Vector4(0, 0, 1, float.NaN), new Vector4(0, 1, 1, float.NaN), new Vector4(0, 1, 0, float.NaN) };
+            }
 
             mlo.AddPortal(portal);
 
@@ -2522,7 +2532,7 @@ namespace CodeWalker.Project
         }
         public void NewMloEntitySet(MCMloEntitySet copy = null)
         {
-            var mlo = CurrentMloRoom?.OwnerMlo ?? CurrentMloPortal?.OwnerMlo ?? CurrentMloEntitySet?.OwnerMlo ?? (CurrentEntity?.MloParent.Archetype as MloArchetype);
+            var mlo = CurrentMloRoom?.OwnerMlo ?? CurrentMloPortal?.OwnerMlo ?? CurrentMloEntitySet?.OwnerMlo ?? (CurrentEntity?.MloParent.Archetype as MloArchetype) ?? (CurrentArchetype as MloArchetype);
             if (mlo == null) return;
 
             if (copy == null)
@@ -2546,6 +2556,7 @@ namespace CodeWalker.Project
             var mloInstance = TryGetMloInstance(mlo);
             if (mloInstance != null)
             {
+                mloInstance.AddEntitySet(set);
             }
 
             LoadProjectTree();
@@ -2617,9 +2628,13 @@ namespace CodeWalker.Project
             MloInstanceData mloInstance = CurrentEntity.MloParent.MloInstance;
             if (mloInstance == null) return false;
 
-            var ent = CurrentEntity;
-            var mcEnt = mloInstance.TryGetArchetypeEntity(ent);
+
+            var delent = CurrentEntity; //CurrentEntity could get changed when we remove the tree node..
+            var delytyp = CurrentEntity.MloParent.Archetype.Ytyp;
+            var mcEnt = mloInstance.TryGetArchetypeEntity(CurrentEntity);
+
             ProjectExplorer?.RemoveMloEntityTreeNode(mcEnt);
+            ProjectExplorer?.SetYtypHasChanged(delytyp, true);
 
             try
             {
@@ -2627,13 +2642,15 @@ namespace CodeWalker.Project
                 {
                     lock (WorldForm.RenderSyncRoot) //don't try to do this while rendering...
                     {
-                        mloInstance.DeleteEntity(ent);
+                        mloArchetype.RemoveEntity(delent);
+                        mloInstance.DeleteEntity(delent);
                         //WorldForm.SelectItem(null, null, null);
                     }
                 }
                 else
                 {
-                    mloInstance.DeleteEntity(ent);
+                    mloArchetype.RemoveEntity(delent);
+                    mloInstance.DeleteEntity(delent);
                 }
             }
             catch (Exception e) // various failures could happen so we'll use a trycatch for when an exception is thrown.
@@ -2642,13 +2659,10 @@ namespace CodeWalker.Project
                 return false;
             }
 
-            var delent = ent;
-            var delytyp = delent.MloParent.Archetype.Ytyp;
-
-            ProjectExplorer?.SetYtypHasChanged(delytyp, true);
 
             ClosePanel((EditYmapEntityPanel p) => { return p.Tag == delent; });
             CurrentEntity = null;
+            CurrentMloEntity = null;
             WorldForm.SelectItem(null);
 
             return true;
@@ -2670,6 +2684,11 @@ namespace CodeWalker.Project
             {
             }
 
+            ProjectExplorer?.RemoveMloRoomTreeNode(CurrentMloRoom);
+            ProjectExplorer?.SetYtypHasChanged(mlo.Ytyp, true);
+            ClosePanel((EditYtypMloRoomPanel p) => { return p.Tag == CurrentMloRoom; });
+            CurrentMloRoom = null;
+
             return true;
         }
         public bool DeleteMloPortal()
@@ -2689,6 +2708,11 @@ namespace CodeWalker.Project
             {
             }
 
+            ProjectExplorer?.RemoveMloPortalTreeNode(CurrentMloPortal);
+            ProjectExplorer?.SetYtypHasChanged(mlo.Ytyp, true);
+            ClosePanel((EditYtypMloPortalPanel p) => { return p.Tag == CurrentMloPortal; });
+            CurrentMloPortal = null;
+
             return true;
         }
         public bool DeleteMloEntitySet()
@@ -2706,8 +2730,14 @@ namespace CodeWalker.Project
             var mloInstance = TryGetMloInstance(mlo);
             if (mloInstance != null)
             {
+                mloInstance.DeleteEntitySet(CurrentMloEntitySet);
             }
 
+            ProjectExplorer?.RemoveMloEntitySetTreeNode(CurrentMloEntitySet);
+            ProjectExplorer?.SetYtypHasChanged(mlo.Ytyp, true);
+            ClosePanel((EditYtypMloEntSetPanel p) => { return p.Tag == CurrentMloEntitySet; });
+            CurrentMloEntitySet = null;
+
             return true;
         }
 
diff --git a/Rendering/Renderer.cs b/Rendering/Renderer.cs
index 3b88ce4..05d014f 100644
--- a/Rendering/Renderer.cs
+++ b/Rendering/Renderer.cs
@@ -1958,12 +1958,13 @@ namespace CodeWalker.Rendering
             }
             if (ent.MloInstance.EntitySets != null)
             {
-                foreach (var entitysets in ent.MloInstance.EntitySets)
+                for (int e = 0; e < ent.MloInstance.EntitySets.Length; e++)
                 {
-                    var entityset = entitysets.Value;
+                    var entityset = ent.MloInstance.EntitySets[e];
                     if (!entityset.VisibleOrForced) continue;
 
                     var entities = entityset.Entities;
+                    if (entities == null) continue;
                     for (int i = 0; i < entities.Count; i++)
                     {
                         var intent = entities[i];
diff --git a/WorldForm.cs b/WorldForm.cs
index bc9ef0f..3571735 100644
--- a/WorldForm.cs
+++ b/WorldForm.cs
@@ -5304,7 +5304,7 @@ namespace CodeWalker
             }
             else
             {
-                //project not open, or entity not selected there, just remove the entity from the ymap/nlo...
+                //project not open, or entity not selected there, just remove the entity from the ymap/mlo...
                 var ymap = ent.Ymap;
                 var instance = ent.MloParent?.MloInstance;
                 if (ymap == null)