During the Main Phase, if your opponent Normal or Special Summoned 5 or more monsters this turn (Quick Effect): You can Tribute as many face-up monsters on the field as possible, and if you do, Special Summon this card from your hand, then Special Summon 1 "Primal Being Token" (Rock/LIGHT/Level 11/ATK ?/DEF ?) to your opponent's field. (This Token's ATK/DEF become the combined original ATK/DEF of the Tributed monsters.) You can only use this effect of "Nibiru, the Primal Being" once per turn.
