diff --git a/PKHeX.Core/Legality/Areas/EncounterArea2.cs b/PKHeX.Core/Legality/Areas/EncounterArea2.cs
index ce93daeeb..5a32fbaf1 100644
--- a/PKHeX.Core/Legality/Areas/EncounterArea2.cs
+++ b/PKHeX.Core/Legality/Areas/EncounterArea2.cs
@@ -196,9 +196,9 @@ private static List<EncounterArea2> GetAreas2Fishing(byte[] data, ref int ofs)
             }
 
             // Read TimeFishGroups
-            var dl = new List<DexLevel>();
+            var dl = new List<SlotTemplate>();
             while (ofs < data.Length)
-                dl.Add(new DexLevel { Species = data[ofs++], Level = data[ofs++] });
+                dl.Add(new SlotTemplate(data[ofs++], data[ofs++]));
 
             // Add TimeSlots
             foreach (var area in areas)
@@ -228,6 +228,18 @@ private static List<EncounterArea2> GetAreas2Fishing(byte[] data, ref int ofs)
             return areas;
         }
 
+        private readonly struct SlotTemplate
+        {
+            public readonly byte Species;
+            public readonly byte Level;
+
+            public SlotTemplate(byte species, byte level)
+            {
+                Species = species;
+                Level = level;
+            }
+        }
+
         private static IEnumerable<EncounterArea2> GetAreas2Headbutt(byte[] data, ref int ofs)
         {
             // Read Location Table
diff --git a/PKHeX.Core/Legality/Core.cs b/PKHeX.Core/Legality/Core.cs
index bdc0c6675..6da4cbef9 100644
--- a/PKHeX.Core/Legality/Core.cs
+++ b/PKHeX.Core/Legality/Core.cs
@@ -686,19 +686,16 @@ internal static EvoCriteria GetBaseSpecies(PKM pkm, int skipOption = 0, int gene
 
         internal static EvoCriteria GetBaseSpecies(PKM pkm, IReadOnlyList<EvoCriteria> evos, int skipOption = 0) => GetBaseSpecies(pkm.Species, evos, skipOption);
 
-        private static readonly EvoCriteria Nincada = new EvoCriteria
+        private static readonly EvoCriteria Nincada = new EvoCriteria(290, 0)
         {
             Method = (int)EvolutionType.LevelUp,
             MinLevel = 20, Level = 20,
             RequiresLvlUp = true,
-            Species = 290, Form = 0,
         };
 
-        private static readonly EvoCriteria EvoEmpty = new EvoCriteria
+        private static readonly EvoCriteria EvoEmpty = new EvoCriteria(290, 0)
         {
             Method = (int)EvolutionType.None,
-            Species = 0,
-            Form = 0,
         };
 
         internal static EvoCriteria GetBaseSpecies(int species, IReadOnlyList<EvoCriteria> evos, int skipOption = 0)
diff --git a/PKHeX.Core/Legality/Evolutions/DexLevel.cs b/PKHeX.Core/Legality/Evolutions/DexLevel.cs
index 75679f43f..f050f2c57 100644
--- a/PKHeX.Core/Legality/Evolutions/DexLevel.cs
+++ b/PKHeX.Core/Legality/Evolutions/DexLevel.cs
@@ -5,7 +5,15 @@
     /// </summary>
     public class DexLevel
     {
-        public int Species { get; set; }
+        public readonly int Species;
+        public readonly int Form;
+
         public int Level { get; set; }
+
+        protected DexLevel(int species, int form)
+        {
+            Species = species;
+            Form = form;
+        }
     }
 }
\ No newline at end of file
diff --git a/PKHeX.Core/Legality/Evolutions/EvoCriteria.cs b/PKHeX.Core/Legality/Evolutions/EvoCriteria.cs
index 85059a683..af8985580 100644
--- a/PKHeX.Core/Legality/Evolutions/EvoCriteria.cs
+++ b/PKHeX.Core/Legality/Evolutions/EvoCriteria.cs
@@ -2,9 +2,12 @@
 {
     public sealed class EvoCriteria : DexLevel
     {
+        public EvoCriteria(int species, int form) : base(species, form)
+        {
+        }
+
         public int MinLevel { get; set; }
         public bool RequiresLvlUp { get; set; }
-        public int Form { get; set; } = -1;
         public int Method { get; set; } = -1;
 
         public bool IsTradeRequired => ((EvolutionType) Method).IsTrade();
diff --git a/PKHeX.Core/Legality/Evolutions/EvolutionChain.cs b/PKHeX.Core/Legality/Evolutions/EvolutionChain.cs
index f98667643..6714b53ca 100644
--- a/PKHeX.Core/Legality/Evolutions/EvolutionChain.cs
+++ b/PKHeX.Core/Legality/Evolutions/EvolutionChain.cs
@@ -239,7 +239,7 @@ internal static List<EvoCriteria> GetValidPreEvolutions(PKM pkm, int maxspecieso
             {
                 return new List<EvoCriteria>(1)
                 {
-                    new EvoCriteria { Species = pkm.Species, Level = lvl, MinLevel = lvl },
+                    new EvoCriteria(pkm.Species, pkm.AltForm) { Level = lvl, MinLevel = lvl },
                 };
             }
 
@@ -248,8 +248,8 @@ internal static List<EvoCriteria> GetValidPreEvolutions(PKM pkm, int maxspecieso
             {
                 return new List<EvoCriteria>(2)
                 {
-                    new EvoCriteria { Species = (int)Species.Shedinja, Level = lvl, MinLevel = 20, Form = 0 },
-                    new EvoCriteria { Species = (int)Species.Nincada, Level = lvl, MinLevel = 1, Form = 0 }
+                    new EvoCriteria((int)Species.Shedinja, 0) { Level = lvl, MinLevel = 20 },
+                    new EvoCriteria((int)Species.Nincada, 0) { Level = lvl, MinLevel = 1 },
                 };
             }
 
diff --git a/PKHeX.Core/Legality/Evolutions/EvolutionMethod.cs b/PKHeX.Core/Legality/Evolutions/EvolutionMethod.cs
index a1d9382bc..be3754aee 100644
--- a/PKHeX.Core/Legality/Evolutions/EvolutionMethod.cs
+++ b/PKHeX.Core/Legality/Evolutions/EvolutionMethod.cs
@@ -105,11 +105,9 @@ private bool HasMetLevelIncreased(PKM pkm, int lvl)
 
         public EvoCriteria GetEvoCriteria(int species, int form, int lvl)
         {
-            return new EvoCriteria
+            return new EvoCriteria(species, form)
             {
-                Species = species,
                 Level = lvl,
-                Form = form,
                 Method = Method,
             };
         }
diff --git a/PKHeX.Core/Legality/Evolutions/EvolutionTree.cs b/PKHeX.Core/Legality/Evolutions/EvolutionTree.cs
index 4a90f3c5f..0d3b03b01 100644
--- a/PKHeX.Core/Legality/Evolutions/EvolutionTree.cs
+++ b/PKHeX.Core/Legality/Evolutions/EvolutionTree.cs
@@ -233,7 +233,7 @@ private IEnumerable<int> GetEvolutions(int species, int form)
         private List<EvoCriteria> GetExplicitLineage(PKM pkm, int maxLevel, bool skipChecks, int maxSpeciesOrigin, int minLevel)
         {
             int lvl = maxLevel;
-            var first = new EvoCriteria { Species = pkm.Species, Level = lvl, Form = pkm.AltForm };
+            var first = new EvoCriteria(pkm.Species, pkm.AltForm) { Level = lvl, };
 
             const int maxEvolutions = 3;
             var dl = new List<EvoCriteria>(maxEvolutions) { first };