Tranquil Tar Pit
Land-Plains Swamp (Rare)

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

At the beginning of your end step, if you didn't cast any spells this turn, Tranquil Tar Pit deals 1 damage to you.

3: Tranquil Tar Pit becomes a 2/2 black Cleric creature until end of turn. It's still a land.

Douglas Grant West