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 Beast-Warrior-Type monster in your hand. Once per turn, you can reveal 1 Iron Core of Koa'ki Meiru in your hand to Special Summon 1 Level 4 or lower Koa'ki Meiru monster from your Deck, except Koa'ki Meiru Urnight.