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.