Leonatus the Vengeful

Relentless — Whenever this creature attacks, you may sacrifice a creature. If you do, defending player loses life equal to the sacrificed creature's power.
{1}{b}{b}, sacrifice a creature: Return Leonatus the Vengeful from your graveyard to the battlefield, Its power and toughness is equal to the sacrificed creature's power and toughness.
"I am back for you. Friend."