Salt Pools
Land-Island Swamp (Rare)

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

Salt Pools enters the battlefield tapped unless you pay 3 life.

BB, Tap, Sacrifice Salt Pools: Put a -1/-1 counter on target creature.

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

Douglas Prescott