Black Alley Spy

Spy — {b}{b}, Discard a card (You may cast this
spell for its spy cost. If you do, it enters the battlefield
under an opponent's control.)
At the beginning of your upkeep, if your Black
Alley Spy's owner, you may destroy target
untapped creature. If you don't own Black Alley
Spy, its owner may destroy target untapped
creature you control.