Wrath of the Pandaman

At the beginning of your upkeep, you may choose a legendary creature you control. If you do, choose target creature an opponent controls. Your creature deals damage equal to it's power to that creature. That creature deals damage equal to it's power to you.
Whenever a creature enters the battlefield under an opponents control, you may choose a legendary creature you control. If you do, your creature deals damage equal to it's power to the opponent's creature. That creature deals damage equal to it's powe