You did not say what Lua engine you are using.
You will have to work around this, and have another creature (invisible or a mall npc) handling the event:
Code:function MallNpc(pUnit, Event) pUnit:RegisterEvent("SpawnMonsters", 60000, 0) end function SpawnMonsters(pUnit) pUnit:SpawnCreature(79002, -3546.46, -906.04, 9.41, 6.28, 168, 120000) end RegisterUnitEvent(npcid, 18, MallNpc)