Omastar

When Omastar enters the battlefield, target opponent sacrifices a creature.
{4}{b}{b}: Return Omastar from your graveyard to the battlefield tapped. Activate this ability only any time you could cast a sorcery and only if an opponent lost life this turn.
Attacks by ensnaring its enemy with its tentacles and biting with sharp fangs. Its overly-large shell makes it sluggish.