Mr. Nimbus

At the beginning of combat on your turn, each Merfolk creature you control explores.
(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 the exploring creature, then put the card back or put it into your graveyard.)

Whenever Mr. Nimbus attacks, you may put a land card from your hand onto the battlefield. If you
don't, draw a card.