diff --git a/PKHeX.Core/Legality/Tables/AltFormInfo.cs b/PKHeX.Core/Legality/Tables/AltFormInfo.cs
new file mode 100644
index 000000000..a145bfd2b
--- /dev/null
+++ b/PKHeX.Core/Legality/Tables/AltFormInfo.cs
@@ -0,0 +1,145 @@
+using System.Collections.Generic;
+
+namespace PKHeX.Core
+{
+    public static class AltFormInfo
+    {
+        /// <summary>
+        /// Checks if the form cannot exist outside of a Battle.
+        /// </summary>
+        /// <param name="species">Entity species</param>
+        /// <param name="form">Entity form</param>
+        /// <param name="format">Current generation format</param>
+        /// <returns>True if it can only exist in a battle, false if it can exist outside of battle.</returns>
+        public static bool IsBattleOnlyForm(int species, int form, int format)
+        {
+            if (!BattleOnly.Contains(species))
+                return false;
+
+            // Some species have battle only forms as well as out-of-battle forms (other than base form).
+            switch (species)
+            {
+                case (int)Species.Slowbro when form == 2 && format >= 8: // Only mark Ultra Necrozma as Battle Only
+                case (int)Species.Darmanitan when form == 2 && format >= 8: // this one is OK, Galarian Slowbro (not a Mega)
+                case (int)Species.Zygarde when form < 4: // Zygarde Complete
+                case (int)Species.Mimikyu when form == 2: // Totem disguise Mimikyu
+                case (int)Species.Necrozma when form < 3: // this one is OK, Galarian non-Zen
+                case (int)Species.Minior when form >= 7: // Minior Shields-Down
+                    return false;
+
+                default:
+                    return true;
+            }
+        }
+
+        /// <summary>
+        /// Reverts the Battle Form to the form it would have outside of Battle.
+        /// </summary>
+        /// <remarks>Only call this if you've already checked that <see cref="IsBattleOnlyForm"/> returns true.</remarks>
+        /// <param name="species">Entity species</param>
+        /// <param name="form">Entity form</param>
+        /// <param name="format">Current generation format</param>
+        /// <returns>Suggested alt form value.</returns>
+        public static int GetOutOfBattleForm(int species, int form, int format)
+        {
+            return species switch
+            {
+                (int)Species.Darmanitan => form & 2,
+                (int)Species.Zygarde when format > 6 => 3,
+                (int)Species.Minior => form + 7,
+                _ => 0
+            };
+        }
+
+        /// <summary>
+        /// Checks if the <see cref="form"/> is a fused form, which indicates it cannot be traded away.
+        /// </summary>
+        /// <param name="species">Entity species</param>
+        /// <param name="form">Entity form</param>
+        /// <param name="format">Current generation format</param>
+        /// <returns>True if it is a fused species-form, false if it is not fused.</returns>
+        public static bool IsFusedForm(int species, int form, int format)
+        {
+            return species switch
+            {
+                (int)Species.Kyurem when form != 0 && format >= 5 => true,
+                (int)Species.Necrozma when form != 0 && format >= 7 => true,
+                (int)Species.Calyrex when form != 0 && format >= 8 => true,
+                _ => false
+            };
+        }
+
+        /// <summary>
+        /// Species that have an alternate form that cannot exist outside of battle.
+        /// </summary>
+        private static readonly HashSet<int> BattleForms = new HashSet<int>
+        {
+            (int)Species.Castform,
+            (int)Species.Cherrim,
+            (int)Species.Darmanitan,
+            (int)Species.Meloetta,
+            (int)Species.Aegislash,
+            (int)Species.Xerneas,
+            (int)Species.Zygarde,
+
+            (int)Species.Wishiwashi,
+            (int)Species.Mimikyu,
+
+            (int)Species.Cramorant,
+            (int)Species.Morpeko,
+            (int)Species.Eiscue,
+
+            (int)Species.Zacian,
+            (int)Species.Zamazenta,
+            (int)Species.Eternatus,
+        };
+
+        /// <summary>
+        /// Species that have a mega form that cannot exist outside of battle.
+        /// </summary>
+        /// <remarks>Using a held item to change form during battle, via an in-battle transformation feature.</remarks>
+        private static readonly HashSet<int> BattleMegas = new HashSet<int>
+        {
+            // XY
+            (int)Species.Venusaur, (int)Species.Charizard, (int)Species.Blastoise,
+            (int)Species.Alakazam, (int)Species.Gengar, (int)Species.Kangaskhan, (int)Species.Pinsir,
+            (int)Species.Gyarados, (int)Species.Aerodactyl, (int)Species.Mewtwo,
+
+            (int)Species.Ampharos, (int)Species.Scizor, (int)Species.Heracross, (int)Species.Houndoom, (int)Species.Tyranitar,
+
+            (int)Species.Blaziken, (int)Species.Gardevoir, (int)Species.Mawile, (int)Species.Aggron, (int)Species.Medicham,
+            (int)Species.Manectric, (int)Species.Banette, (int)Species.Absol, (int)Species.Latios, (int)Species.Latias,
+
+            (int)Species.Garchomp, (int)Species.Lucario, (int)Species.Abomasnow,
+
+            // AO
+            (int)Species.Beedrill, (int)Species.Pidgeot, (int)Species.Slowbro,
+
+            (int)Species.Steelix,
+
+            (int)Species.Sceptile, (int)Species.Swampert, (int)Species.Sableye, (int)Species.Sharpedo, (int)Species.Camerupt,
+            (int)Species.Altaria, (int)Species.Glalie, (int)Species.Salamence, (int)Species.Metagross, (int)Species.Rayquaza,
+
+            (int)Species.Lopunny, (int)Species.Gallade,
+            (int)Species.Audino, (int)Species.Diancie,
+
+            // USUM
+            (int)Species.Necrozma, // Ultra Necrozma
+        };
+
+        /// <summary>
+        /// Species that have a primal form that cannot exist outside of battle.
+        /// </summary>
+        private static readonly HashSet<int> BattlePrimals = new HashSet<int> { 382, 383 };
+
+        private static readonly HashSet<int> BattleOnly = GetBattleFormSet();
+
+        private static HashSet<int> GetBattleFormSet()
+        {
+            var hs = new HashSet<int>(BattleForms);
+            hs.UnionWith(BattleMegas);
+            hs.UnionWith(BattlePrimals);
+            return hs;
+        }
+    }
+}
diff --git a/PKHeX.Core/Legality/Tables/Tables.cs b/PKHeX.Core/Legality/Tables/Tables.cs
index 05b474a78..6fdcbb420 100644
--- a/PKHeX.Core/Legality/Tables/Tables.cs
+++ b/PKHeX.Core/Legality/Tables/Tables.cs
@@ -257,58 +257,6 @@ namespace PKHeX.Core
             809, // Melmetal
         };
 
-        /// <summary>
-        /// Species that have an alternate form that cannot exist outside of battle.
-        /// </summary>
-        public static readonly HashSet<int> BattleForms = new HashSet<int>
-        {
-            351, // Castform
-            421, // Cherrim
-            555, // Darmanitan
-            648, // Meloetta
-            681, // Aegislash
-            716, // Xerneas
-            746, // Wishiwashi
-            778, // Mimikyu
-
-            (int)Species.Cramorant,
-            (int)Species.Morpeko,
-            (int)Species.Eiscue,
-
-            (int)Species.Zacian,
-            (int)Species.Zamazenta,
-            (int)Species.Eternatus,
-        };
-
-        /// <summary>
-        /// Species that have a mega form that cannot exist outside of battle.
-        /// </summary>
-        public static readonly HashSet<int> BattleMegas = new HashSet<int>
-        {
-            // XY
-            3,6,9,65,80,
-            115,127,130,142,150,181,
-            212,214,229,248,282,
-            303,306,308,310,354,359,380,381,
-            445,448,460,
-
-            // AO
-            15,18,94,
-            208,254,257,260,
-            302,319,323,334,362,373,376,384,
-            428,475,
-            531,
-            719,
-
-            // USUM
-            800, // Ultra Necrozma
-        };
-
-        /// <summary>
-        /// Species that have a primal form that cannot exist outside of battle.
-        /// </summary>
-        public static readonly HashSet<int> BattlePrimals = new HashSet<int> { 382, 383 };
-
         public static readonly HashSet<int> Z_Moves = new HashSet<int>
         {
             622, 623, 624, 625, 626, 627, 628, 629, 630, 631, 632, 633, 634, 635, 636, 637, 638, 639, 640, 641, 642, 643, 644, 645, 646, 647, 648, 649, 650, 651, 652, 653, 654, 655, 656, 657, 658,
diff --git a/PKHeX.Core/Legality/Verifiers/FormVerifier.cs b/PKHeX.Core/Legality/Verifiers/FormVerifier.cs
index fe301035e..1b8681c7b 100644
--- a/PKHeX.Core/Legality/Verifiers/FormVerifier.cs
+++ b/PKHeX.Core/Legality/Verifiers/FormVerifier.cs
@@ -173,22 +173,16 @@ namespace PKHeX.Core
                     if (form != 0 && pkm.Box > -1 && pkm.Format <= 6) // has form but stored in box
                         return GetInvalid(LFormParty);
                     break;
-
-                // Battle only Forms with other legal forms allowed
-                case (int)Species.Zygarde when form >= 4: // Zygarde Complete
-                case (int)Species.Minior when form < 7: // Minior Shield
-                case (int)Species.Necrozma when form == 3: // Ultra Necrozma
-                    return GetInvalid(LFormBattle);
-                case (int)Species.Necrozma when form < 3: // Necrozma Fused forms & default
-                case (int)Species.Mimikyu when form == 2: // Totem disguise Mimikyu
-                    return VALID;
             }
 
+            var format = pkm.Format;
+            if (AltFormInfo.IsBattleOnlyForm(species, form, format))
+                return GetInvalid(LFormBattle);
+
             if (form == 0)
                 return VALID;
 
             // everything below here is currently an altform
-            var format = pkm.Format;
             if (format >= 7 && Info.Generation < 7)
             {
                 if (species == 25 || Legal.AlolanOriginForms.Contains(species) || Legal.AlolanVariantEvolutions12.Contains(data.EncounterOriginal.Species))
@@ -214,25 +208,9 @@ namespace PKHeX.Core
                 }
             }
 
-            if (IsBattleOnlyForm(species, form, format))
-                return GetInvalid(LFormBattle);
-
             return VALID;
         }
 
-        public static bool IsBattleOnlyForm(int species, int form, int format)
-        {
-            if (!BattleOnly.Contains(species))
-                return false;
-            if (species == (int) Species.Darmanitan && form == 2 && format >= 8)
-                return false; // this one is OK, Galarian non-Zen
-            if (species == (int) Species.Slowbro && form == 2 && format >= 8)
-                return false; // this one is OK, Galarian Slowbro (not a Mega)
-            if (species == (int) Species.Necrozma && form != 3)
-                return false; // Only mark Ultra Necrozma as Battle Only
-            return true;
-        }
-
         public static int GetArceusFormFromHeldItem(int item, int format)
         {
             if (777 <= item && item <= 793)
@@ -260,17 +238,6 @@ namespace PKHeX.Core
             return 0;
         }
 
-        private static readonly HashSet<int> BattleOnly = GetBattleFormSet();
-
-        private static HashSet<int> GetBattleFormSet()
-        {
-            var hs = new HashSet<int>();
-            hs.UnionWith(Legal.BattleForms);
-            hs.UnionWith(Legal.BattleMegas);
-            hs.UnionWith(Legal.BattlePrimals);
-            return hs;
-        }
-
         private static readonly HashSet<int> SafariFloette = new HashSet<int> { 0, 1, 3 }; // 0/1/3 - RBY
 
         private void VerifyFormFriendSafari(LegalityAnalysis data)