Bloody Conquest

Whenever a creature an opponent controls dies, put a body counter on Bloody Conquest. At the beginning of your end step, sacrifice a creature. At the beginning of your upkeep, if there are 20 or more body counters on Bloody Conquest, destroy all creatures your opponents control and remove all body counters from Bloody Conquest
"There is no instance of a nation benefiting from prolonged warfare" -- Sun Tzu