diff --git a/PKHeX.Core/PKM/Util/PKX.cs b/PKHeX.Core/PKM/Util/PKX.cs
index bd1a3c053..e0c9e9c48 100644
--- a/PKHeX.Core/PKM/Util/PKX.cs
+++ b/PKHeX.Core/PKM/Util/PKX.cs
@@ -492,7 +492,7 @@ private static void CryptPKM45(byte[] data, uint pv, uint chk, int blockSize)
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static void CryptArray(byte[] data, uint seed, int start, int end)
+        public static void CryptArray(byte[] data, uint seed, int start, int end)
         {
             for (int i = start; i < end; i += 2)
                 Crypt(data, ref seed, i);
diff --git a/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeForest.cs b/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeForest.cs
new file mode 100644
index 000000000..558d63ee2
--- /dev/null
+++ b/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeForest.cs
@@ -0,0 +1,119 @@
+using System;
+
+namespace PKHeX.Core
+{
+    public class EntreeForest
+    {
+        /// <summary>
+        /// Areas 1 thru 8 have 20 slots.
+        /// </summary>
+        private const byte Count18 = 20;
+
+        /// <summary>
+        /// 9th Area has only 10 slots.
+        /// </summary>
+        private const byte Count9 = 10;
+
+        private const int TotalSlots = Count18 + (3 * 8 * Count18) + (3 * Count9);
+
+        /// <summary>
+        /// Areas 3 thru 8 can be unlocked (set a value 0 to 6).
+        /// </summary>
+        private const byte MaxUnlock38Areas = 6;
+
+
+        private readonly byte[] Data;
+
+        public EntreeForest(byte[] data)
+        {
+            Data = data;
+            PKX.CryptArray(data, EncryptionSeed, 0, data.Length);
+        }
+        public byte[] Write()
+        {
+            byte[] data = (byte[])Data.Clone();
+            PKX.CryptArray(data, EncryptionSeed, 0, data.Length);
+            return data;
+        }
+
+        /// <summary>
+        /// Gets all Entree Slot data.
+        /// </summary>
+        public EntreeSlot[] Slots
+        {
+            get
+            {
+                var slots = new EntreeSlot[TotalSlots];
+                for (int i = 0; i < slots.Length; i++)
+                    slots[i] = new EntreeSlot(Data, i * 4) { Area = GetSlotArea(i) };
+                return slots;
+            }
+        }
+
+        /// <summary>
+        /// Determines if the 9th Area is available to enter.
+        /// </summary>
+        public bool Unlock9thArea
+        {
+            get => Data[0x848] == 1;
+            set => Data[0x848] = (byte)(value ? 1 : 0);
+        }
+
+        /// <summary>
+        /// Determines how many extra areas are available to enter. Areas 1 & 2 are already available by default.
+        /// </summary>
+        public int Unlock38Areas
+        {
+            get => Data[0x849];
+            set => Data[0x849] = (byte)Math.Max(MaxUnlock38Areas, value);
+        }
+
+        public uint EncryptionSeed
+        {
+            get => BitConverter.ToUInt32(Data, 0x84C);
+            private set => BitConverter.GetBytes(value).CopyTo(Data, 0x84C);
+        }
+        public void UnlockAllAreas()
+        {
+            Unlock38Areas = MaxUnlock38Areas;
+            Unlock9thArea = true;
+        }
+
+        public void DeleteAll()
+        {
+            foreach (var e in Slots)
+                e.Delete();
+        }
+
+        private static EntreeForestArea GetSlotArea(int index)
+        {
+            if (index < Count18)
+                return EntreeForestArea.Deepest;
+            index -= Count18;
+
+            const int slots9 = 3 * Count9;
+            if (index < slots9)
+                return EntreeForestArea.Ninth | GetSlotPosition(index / Count9);
+            index -= slots9;
+
+            const int slots18 = 3 * Count18;
+            int area = index / slots18;
+            if (area >= 8)
+                throw new ArgumentOutOfRangeException(nameof(index));
+            index %= slots18;
+
+            return (EntreeForestArea)((int)EntreeForestArea.First << area) | GetSlotPosition(index / Count18);
+        }
+
+        private static EntreeForestArea GetSlotPosition(int index)
+        {
+            switch (index)
+            {
+                case 0: return EntreeForestArea.Center;
+                case 1: return EntreeForestArea.Left;
+                case 2: return EntreeForestArea.Right;
+                default: throw new ArgumentOutOfRangeException();
+            }
+        }
+    }
+}
diff --git a/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeForestArea.cs b/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeForestArea.cs
new file mode 100644
index 000000000..5349ebe90
--- /dev/null
+++ b/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeForestArea.cs
@@ -0,0 +1,23 @@
+using System;
+
+namespace PKHeX.Core
+{
+    [Flags]
+    public enum EntreeForestArea
+    {
+        Deepest = 1 << 0,
+        First =   1 << 1,
+        Second =  1 << 2,
+        Third =   1 << 3,
+        Fourth =  1 << 4,
+        Fifth =   1 << 5,
+        Sixth =   1 << 6,
+        Seventh = 1 << 7,
+        Eighth =  1 << 8,
+        Ninth =   1 << 9,
+
+        Left =    1 << 10,
+        Right =   1 << 11,
+        Center =  1 << 12,
+    }
+}
\ No newline at end of file
diff --git a/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeSlot.cs b/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeSlot.cs
new file mode 100644
index 000000000..3aa56711a
--- /dev/null
+++ b/PKHeX.Core/Saves/Substructures/EntreeForest/EntreeSlot.cs
@@ -0,0 +1,57 @@
+using System;
+
+namespace PKHeX.Core
+{
+    public class EntreeSlot
+    {
+        public int Species // bits 0-10
+        {
+            get => (int)(RawValue & 0x7FF) >> 0;
+            set => RawValue = (RawValue & 0xFFFF_F800) | ((uint)value << 0);
+        }
+        public int Move // bits 11-20
+        {
+            get => (int)(RawValue & 0x1F_F800) >> 10;
+            set => RawValue = (RawValue & 0xFFF0_02FF) | ((uint)value << 10);
+        }
+        public int Gender // bits 21-22
+        {
+            get => (int)(RawValue & 60_0000) >> 21;
+            set => RawValue = (RawValue & 0xFF9F_FFFF) | ((uint)value << 21);
+        }
+        public int Form // bits 23-27
+        {
+            get => (int)(RawValue & 0x0F80_0000) >> 23;
+            set => RawValue = (RawValue & 0xF07F_FFFF) | ((uint)value << 23);
+        }
+        public bool Invisible // bit 28
+        {
+            get => ((RawValue >> 28) & 1) == 1;
+            set => RawValue = (RawValue & 0xEFFFFFFF) | (value ? 0 : 1u << 28);
+        }
+        public int Animation // bits 29-31
+        {
+            get => (int)(RawValue >> 29);
+            set => RawValue = (RawValue << 3) >> 3 | (uint)(value << 29);
+        }
+
+        private readonly byte[] Data;
+        private readonly int Offset;
+
+        public uint RawValue
+        {
+            get => BitConverter.ToUInt32(Data, Offset);
+            set => BitConverter.GetBytes(value).CopyTo(Data, Offset);
+        }
+
+        public void Delete() => RawValue = 0;
+
+        public EntreeForestArea Area { get; internal set; }
+
+        public EntreeSlot(byte[] data, int ofs)
+        {
+            Data = data;
+            Offset = ofs;
+        }
+    }
+}
\ No newline at end of file