Umbral Allegiance

Each {b} in the mana cost of creature cards in your graveyard adds one to your devotion to black.
At the beginning of your end step, if your
devotion to black is twelve or greater, each
opponent sacrifices a creature, then return up to
one target creature from an opponent's graveyard to the battlefield under your control.
Embrace the Night. Only She can grant you power to
match your ambitions.