Mistveil Ruins
Land-Plains Swamp (Rare)

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

Mistveil Ruins enters the battlefield tapped unless you control one or more creatures.

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

BB, Tap, Sacrifice Mistveil Ruins: Put a -1/-1 counter on target creature.

Douglas Moeller