Ursula, the Sea Witch

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 Ursula attacks, you may put a land
card from your hand onto the battlefield.
If you don't, draw a card, you poor unfortunate soul.