The North Remembers

(Start the game with this conspiracy face up in the command zone.)
Whenever one or more creatures deal combat damage to you, you may put a memory counter on that creature's controller.

At the beginning of your endstep you may remove all memory counters from players, for each memory counter on each opponent, that player loses 2 life, discards a card, or sacrifices a permanent. This ability may only be used once per game.