Seeker of Mul Daya

You may exert Seeker of Mul Daya as it attacks. When you do, it explores. (An exerted creature won't untap during your next untap step. Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)