During each of your End Phases, destroy this card unless you send 1 'Iron Core of Koa'ki Meiru' from your hand to the Graveyard or reveal 1 Zombie-Type monster in your hand. If a 'Koa'ki Meiru' monster you control would be destroyed by battle or by a card effect, you can remove from play 1 'Koa'ki Meiru' monster in your Graveyard instead.