Kayren,Will of the Rivertide

When Kayren,Will of the Rivertide becomes tapped, you may pay {2}. If you do, look at the top card of your library, if it's a Merfolk card, reveal it and add it to your hand. Otherwise,
put it at the bottom of you library.
Return a tapped creature you control to it's owner's hand: Target Merfolk gets +1/+1 and gains Islandwalk until end of turn.