Arcanum, Dragon Monarch

Flying

At the beginning of your second main phase on your turn, you may exile up to X cards from the top of your library, where X is the greatest power among creatures you control. You may play those cards as long as you control Arcanum.

When Arcanum leaves the battlefield, you may put 1 card exiled with it into your hand, then put the rest on the bottom of your library in a random order.