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".