diff --git a/PKHeX/Legality/CheckStrings.cs b/PKHeX/Legality/CheckStrings.cs
index 43320f82f..05971f343 100644
--- a/PKHeX/Legality/CheckStrings.cs
+++ b/PKHeX/Legality/CheckStrings.cs
@@ -241,6 +241,7 @@ public static string[] getLocalization(string[] existingLines = null)
         public static string V110 {get; set;} = "Ability does not match Mystery Gift.";
         public static string V111 {get; set;} = "Hidden Ability on non-SOS wild encounter.";
         public static string V112 {get; set;} = "Hidden Ability not available.";
+        public static string V217 {get; set;} = "Hidden Grotto captures should have Hidden Ability.";
 
         public static string V115 {get; set;} = "Ability matches ability number."; // Valid
         public static string V113 {get; set;} = "Ability does not match PID.";
diff --git a/PKHeX/Legality/Checks.cs b/PKHeX/Legality/Checks.cs
index 92501bc8b..63a57c3fd 100644
--- a/PKHeX/Legality/Checks.cs
+++ b/PKHeX/Legality/Checks.cs
@@ -985,6 +985,17 @@ private void verifyAbility()
                         return;
                     }
                 }
+                if (pkm.GenNumber == 5)
+                {
+                    if (EncounterType == typeof(EncounterSlot[]) && !((EncounterSlot[])EncounterMatch).Any(slot => slot.Type != SlotType.HiddenGrotto)) //encounter only at HiddenGrotto
+                    {
+                        if (pkm.AbilityNumber != 4)
+                        {
+                            AddLine(Severity.Invalid, V217, CheckIdentifier.Ability);
+                            return;
+                        }
+                    }
+                }
                 if (pkm.GenNumber == 6)
                 {
                     if (EncounterIsMysteryGift)
diff --git a/PKHeX/Legality/Core.cs b/PKHeX/Legality/Core.cs
index d69418a5a..1a58199f9 100644
--- a/PKHeX/Legality/Core.cs
+++ b/PKHeX/Legality/Core.cs
@@ -247,10 +247,7 @@ private static void MarkB2W2SwarmSlots(ref EncounterArea[] Areas)
         private static void MarkG5HiddenGrottoSlots(ref EncounterArea[] Areas)
         {
             foreach (EncounterSlot s in Areas[0].Slots) //Only 1 area
-            {
                 s.Type = SlotType.HiddenGrotto; 
-                //todo: Ability marking and checking
-            }
         }
         private static void MarkG5Slots(ref EncounterArea[] Areas)
         {
diff --git a/PKHeX/Resources/text/en/legality_en.txt b/PKHeX/Resources/text/en/legality_en.txt
index 95f4363c4..352f34b57 100644
Binary files a/PKHeX/Resources/text/en/legality_en.txt and b/PKHeX/Resources/text/en/legality_en.txt differ
diff --git a/PKHeX/Resources/text/zh/legality_zh.txt b/PKHeX/Resources/text/zh/legality_zh.txt
index 8edb97543..d41cb0bbf 100644
--- a/PKHeX/Resources/text/zh/legality_zh.txt
+++ b/PKHeX/Resources/text/zh/legality_zh.txt
@@ -143,6 +143,7 @@ V109 = 特性被特性胶囊改变。
 V110 = 特性与神秘礼物不一致。
 V111 = 非帮手宝可梦拥有隐藏特性。
 V112 = 隐藏特性不可获得。
+v217 = 隐藏洞穴捕获的宝可梦必定为隐藏特性。
 V115 = 特性与特性值一致。
 V113 = 特性与PID不一致。
 V114 = 特性与特性值不一致。