Peat Vents
Land-Island Swamp (Rare)

(Tap: Add U or B to your mana pool.)

When Peat Vents enters the battlefield, return a land you control to its owner's hand.

BB, Tap, Sacrifice Peat Vents: Put a -1/-1 counter on target creature.

2, Tap: Target land becomes a 3/3 blue Merfolk creature until end of turn. It's still a land.

Jason Palck