Herbert West, Re-Animator

Whenever another nontoken creature dies for the first time each turn, create a Serum token. (It's
an artifact with "{2}, {t}, Sacrifice this artifact: Regenerate target creature.")

{t}, Sacrifice three Serums: Return target creature card from your graveyard to the battlefield with a finality counter on it. It gains haste until end of
turn. (If a creature with a finality counter on it would die, exile it instead.)