Kodama of the Cataclysm

Defender
At the beginning of each player's upkeep, that player may sacrifice a creature. If that player doesn't, his or her life total becomes equal to Kodama of the Cataclysm's toughness.
Sacrifice X creatures: Return Kodama from its owner's graveyard to the battlefield under your control, then put X -1/-1 counters on it. Any player may activate this ability.