At the beginning of your end step, sacrifice each other creature you control.
Discard two cards, Sacrifice Plague Reaver: Choose target opponent. Return Plague Reaver to the battlefield under that player's control at the beginning of their next upkeep.
If Plague Reaver is put onto the battlefield under the control of someone other than its owner, and that player leaves the game, Plague Reaver is exiled.
If the chosen opponent leaves the game after the activated ability resolves but before the delayed triggered ability returns Plague Reaver to the battlefield, Plague Reaver stays in the graveyard.