Vundra's Contract Circle

At the end of each turn, if a creature has been damaged, put a 0/2 succubus token into play
with "Soul bondage" (tap X succubi, target creature receives X damage. where X is half the total power of creatures you tapped, rounded down. if a creature
would die this way, return it to the battlefield under
your control except it is a Black Demon in addition
to its colors and types)