Acererak the Archlich is a mythic Legendary Creature — Zombie Wizard card from Secret Lair Drop (SLD), collector number 1784. Current market price: $13.09, TCGplayer market prices via Scryfall.
When Acererak enters, if you haven't completed Tomb of Annihilation, return Acererak to its owner's hand and venture into the dungeon. Whenever Acererak attacks, for each opponent, you create a 2/2 black Zombie creature token unless that player sacrifices a creature of their choice.