Koa’ki Meiru Guardian (BP03-EN056)

During each of your End Phases, destroy this card unless you send 1 "Iron Core of Koa'ki Meiru" from your hand to the GY or reveal 1 Rock monster in your hand. When a monster effect is activated (Quick Effect): You can Tribute this card; negate the activation, and if you do, destroy that monster.

Rock / Effect, Battle Pack 3: Monster League