diff --git a/Content.Server/Humanoid/Systems/RandomHumanoidSystem.cs b/Content.Server/Humanoid/Systems/RandomHumanoidSystem.cs
index 4ae69d2fd7c..c9cfbdd43f0 100644
--- a/Content.Server/Humanoid/Systems/RandomHumanoidSystem.cs
+++ b/Content.Server/Humanoid/Systems/RandomHumanoidSystem.cs
@@ -40,7 +40,7 @@ public EntityUid SpawnRandomHumanoid(string prototypeId, EntityCoordinates coord
         if (!_prototypeManager.TryIndex<RandomHumanoidSettingsPrototype>(prototypeId, out var prototype))
             throw new ArgumentException("Could not get random humanoid settings");
 
-        var profile = HumanoidCharacterProfile.Random(prototype.SpeciesBlacklist);
+        var profile = HumanoidCharacterProfile.Random(prototype.SpeciesBlacklist, false); // MACRO
         var speciesProto = _prototypeManager.Index<SpeciesPrototype>(profile.Species);
         var humanoid = EntityManager.CreateEntityUninitialized(speciesProto.Prototype, coordinates);
 
diff --git a/Content.Shared/Humanoid/Prototypes/SpeciesPrototype.cs b/Content.Shared/Humanoid/Prototypes/SpeciesPrototype.cs
index 03cabf19d09..8803d019edc 100644
--- a/Content.Shared/Humanoid/Prototypes/SpeciesPrototype.cs
+++ b/Content.Shared/Humanoid/Prototypes/SpeciesPrototype.cs
@@ -105,6 +105,21 @@ public sealed partial class SpeciesPrototype : IPrototype
     /// </summary>
     [DataField]
     public int MaxAge = 120;
+
+    // MACRO start
+    /// <summary>
+    /// Whether or not the species is available for randomization.
+    /// </summary>
+    [DataField]
+    public bool RandomViable { get; private set; }
+
+    /// <summary>
+    /// When a random species is picked, verify random float is lower than this number
+    /// if not, don't pick the species
+    /// </summary>
+    [DataField]
+    public float RandomChance { get; private set; } = 1f;
+    // MACRO end
 }
 
 public enum SpeciesNaming : byte
diff --git a/Content.Shared/Preferences/HumanoidCharacterProfile.cs b/Content.Shared/Preferences/HumanoidCharacterProfile.cs
index 7dfd21e7182..428c760584f 100644
--- a/Content.Shared/Preferences/HumanoidCharacterProfile.cs
+++ b/Content.Shared/Preferences/HumanoidCharacterProfile.cs
@@ -214,19 +214,29 @@ public static HumanoidCharacterProfile DefaultWithSpecies(ProtoId<SpeciesPrototy
         }
 
         // TODO: This should eventually not be a visual change only.
-        public static HumanoidCharacterProfile Random(HashSet<string>? ignoredSpecies = null)
+        // MACRO start, extensive changes.
+        public static HumanoidCharacterProfile Random(HashSet<string>? speciesBlacklist = null, bool? characterCreation = true)
         {
             var prototypeManager = IoCManager.Resolve<IPrototypeManager>();
             var random = IoCManager.Resolve<IRobustRandom>();
 
             var species = random.Pick(prototypeManager
                 .EnumeratePrototypes<SpeciesPrototype>()
-                .Where(x => ignoredSpecies == null ? x.RoundStart : x.RoundStart && !ignoredSpecies.Contains(x.ID))
+                .Where(x =>
+                {
+                    if (speciesBlacklist != null && speciesBlacklist.Contains(x.ID))
+                        return false;
+                    if (characterCreation == true)
+                        return x.RoundStart;
+                    return random.NextFloat() < x.RandomChance && x.RandomViable;
+                })
                 .ToArray()
-            ).ID;
+            )
+            .ID;
 
             return RandomWithSpecies(species);
         }
+        // MACRO end
 
         public static HumanoidCharacterProfile RandomWithSpecies(string? species = null)
         {
diff --git a/Resources/Prototypes/Species/arachnid.yml b/Resources/Prototypes/Species/arachnid.yml
index 10d838d01df..8bce0e5570f 100644
--- a/Resources/Prototypes/Species/arachnid.yml
+++ b/Resources/Prototypes/Species/arachnid.yml
@@ -2,6 +2,7 @@
   id: Arachnid
   name: species-name-arachnid
   roundStart: true
+  randomViable: true # MACRO
   prototype: MobArachnid
   defaultSkinTone: "#385878"
   dollPrototype: AppearanceArachnid
diff --git a/Resources/Prototypes/Species/diona.yml b/Resources/Prototypes/Species/diona.yml
index 880cdfdf84e..311e13a9c4e 100644
--- a/Resources/Prototypes/Species/diona.yml
+++ b/Resources/Prototypes/Species/diona.yml
@@ -2,6 +2,7 @@
   id: Diona
   name: species-name-diona
   roundStart: true
+  randomViable: true # MACRO
   prototype: MobDiona
   defaultSkinTone: "#cdb369"
   dollPrototype: AppearanceDiona
diff --git a/Resources/Prototypes/Species/dwarf.yml b/Resources/Prototypes/Species/dwarf.yml
index 0c2fbaf8b63..35f6bcb7950 100644
--- a/Resources/Prototypes/Species/dwarf.yml
+++ b/Resources/Prototypes/Species/dwarf.yml
@@ -2,6 +2,7 @@
   id: Dwarf
   name: species-name-dwarf
   roundStart: true
+  randomViable: true # MACRO
   prototype: MobDwarf
   dollPrototype: AppearanceDwarf
   skinColoration: HumanToned
diff --git a/Resources/Prototypes/Species/human.yml b/Resources/Prototypes/Species/human.yml
index 24c18c00dea..38112d6f3bb 100644
--- a/Resources/Prototypes/Species/human.yml
+++ b/Resources/Prototypes/Species/human.yml
@@ -2,6 +2,7 @@
   id: Human
   name: species-name-human
   roundStart: true
+  randomViable: true # MACRO
   prototype: MobHuman
   dollPrototype: AppearanceHuman
   skinColoration: HumanToned
diff --git a/Resources/Prototypes/Species/moth.yml b/Resources/Prototypes/Species/moth.yml
index 0e6fcd244a0..72e7135292d 100644
--- a/Resources/Prototypes/Species/moth.yml
+++ b/Resources/Prototypes/Species/moth.yml
@@ -2,6 +2,7 @@
   id: Moth
   name: species-name-moth
   roundStart: true
+  randomViable: true # MACRO
   prototype: MobMoth
   defaultSkinTone: "#ffda93"
   dollPrototype: AppearanceMoth
diff --git a/Resources/Prototypes/Species/reptilian.yml b/Resources/Prototypes/Species/reptilian.yml
index d8491a6aec9..81bc9cb0161 100644
--- a/Resources/Prototypes/Species/reptilian.yml
+++ b/Resources/Prototypes/Species/reptilian.yml
@@ -2,6 +2,7 @@
   id: Reptilian
   name: species-name-reptilian
   roundStart: true
+  randomViable: true # MACRO
   prototype: MobReptilian
   defaultSkinTone: "#34a223"
   dollPrototype: AppearanceReptilian
diff --git a/Resources/Prototypes/Species/slime.yml b/Resources/Prototypes/Species/slime.yml
index 5c3624731eb..ce814fcd2d6 100644
--- a/Resources/Prototypes/Species/slime.yml
+++ b/Resources/Prototypes/Species/slime.yml
@@ -2,6 +2,7 @@
   id: SlimePerson
   name: species-name-slime
   roundStart: true
+  randomViable: true # MACRO
   prototype: MobSlimePerson
   defaultSkinTone: "#b8b8b8"
   dollPrototype: AppearanceSlimePerson
diff --git a/Resources/Prototypes/Species/vox.yml b/Resources/Prototypes/Species/vox.yml
index 3a543caca15..91d5467ca57 100644
--- a/Resources/Prototypes/Species/vox.yml
+++ b/Resources/Prototypes/Species/vox.yml
@@ -2,6 +2,7 @@
   id: Vox
   name: species-name-vox
   roundStart: true
+  randomViable: true # MACRO
   prototype: MobVox
   dollPrototype: AppearanceVox
   skinColoration: VoxFeathers