G'chsi, the Possessor

When G'chsi comes into play, gain control of target creature. During your upkeep, place a
-1/-1 token on said creature. Whenever the creature goes into the controller's graveyard, gain control of target creature. (You still place -1/-1 tokens on the creature during your upkeep.)
His hunger insatiable, his lust for power unchecked...