Countdown to Catastrophe

Whenever a source you control destroys a
legendary creature an opponent controls, put a
chaos counter on that creature's controller. At
the beginning of your upkeep each turn, if a
player has 4 or more chaos counters, they lose
the game.
"You want me to do something, Arlo? Fine, I will.
I'll start by tearing down your precious system.
I'm going to break the hierarchy. How's that?"
—Joker