fix(Core/BWL): Victor Nefarius encounter not resetting properly (#11145)

src/server/scripts/EasternKingdoms/BlackrockMountain/BlackwingLair/boss_nefarian.cpp

@@ -468,6 +468,8 @@ public:
                 me->SetUInt32Value(UNIT_NPC_FLAGS, 0);
                 me->SetStandState(UNIT_STAND_STATE_STAND);
                 me->SetFlag(UNIT_FIELD_FLAGS, UNIT_FLAG_IMMUNE_TO_PC | UNIT_FLAG_NOT_SELECTABLE);
+                // Due to Nefarius despawning himself on Vael, we need to update the guid on instance to prevent unwanted behaviours as encounter not resetting at all.
+                instance->SetGuidData(DATA_LORD_VICTOR_NEFARIUS, me->GetGUID());
             }
         }
 

src/server/scripts/EasternKingdoms/BlackrockMountain/BlackwingLair/instance_blackwing_lair.cpp

@@ -357,6 +357,18 @@ public:
             return ObjectGuid::Empty;
         }
 
+        void SetGuidData(uint32 type, ObjectGuid data) override
+        {
+            switch (type)
+            {
+                case DATA_LORD_VICTOR_NEFARIUS:
+                    victorNefariusGUID = data;
+                    break;
+                default:
+                    break;
+            }
+        }
+
         void OnUnitDeath(Unit* unit) override
         {
             switch (unit->GetEntry())