Core/XP: Players only get 10% xp for killing NPCs of the same expansion or lower.

src/server/game/DataStores/DBCStores.cpp

@@ -862,6 +862,24 @@ uint32 GetVirtualMapForMapAndZone(uint32 mapid, uint32 zoneId)
     return mapid;
 }
 
+uint32 GetMaxLevelForExpansion(uint32 expansion)
+{
+    switch (expansion)
+    {
+        case CONTENT_1_60:
+            return 60;
+        case CONTENT_61_70:
+            return 70;
+        case CONTENT_71_80:
+            return 80;
+        case CONTENT_81_85:
+            return 85;
+        default:
+            break;
+    }
+    return 0;
+}
+
 /*
 Used only for calculate xp gain by content lvl.
 Calculation on Gilneas and group maps of LostIslands calculated as CONTENT_1_60.

src/server/game/DataStores/DBCStores.h

@@ -52,6 +52,8 @@ enum ContentLevels
     MAX_CONTENT
 };
 
+uint32 GetMaxLevelForExpansion(uint32 expansion);
+
 ContentLevels GetContentLevelsForMapAndZone(uint32 mapid, uint32 zoneId);
 
 bool IsTotemCategoryCompatiableWith(uint32 itemTotemCategoryId, uint32 requiredTotemCategoryId);

src/server/game/Entities/Player/Player.cpp

@@ -75,6 +75,7 @@
 #include <cmath>
 #include "AccountMgr.h"
 #include "DB2Stores.h"
+#include "DBCStores.h"
 #include "Battlefield.h"
 #include "BattlefieldMgr.h"
 #include "BattlefieldWG.h"
@@ -513,10 +514,14 @@ inline void KillRewarder::_RewardXP(Player* player, float rate)
         for (Unit::AuraEffectList::const_iterator i = auras.begin(); i != auras.end(); ++i)
             AddPct(xp, (*i)->GetAmount());
 
-        // 4.2.3. Give XP to player.
+        // 4.2.3. Calculate expansion penalty
+        if (_victim->GetTypeId() == TYPEID_UNIT && player->GetLevel() >= GetMaxLevelForExpansion(_victim->ToCreature()->GetCreatureTemplate()->expansion))
+            xp = CalculatePct(xp, 10); // Players get only 10% xp for killing creatures of lower expansion levels than himself
+        
+        // 4.2.4. Give XP to player.
         player->GiveXP(xp, _victim, _groupRate);
         if (Pet* pet = player->GetPet())
-            // 4.2.4. If player has pet, reward pet with XP (100% for single player, 50% for group case).
+            // 4.2.5. If player has pet, reward pet with XP (100% for single player, 50% for group case).
             pet->GivePetXP(_group ? xp / 2 : xp);
     }
 }