Relentless Dead is a mythic Creature — Zombie card from Secret Lair Drop (SLD), collector number 850. Current market price: — (foil $18.27), TCGplayer market prices via Scryfall.
Menace (This creature can't be blocked except by two or more creatures.) When this creature dies, you may pay {B}. If you do, return it to its owner's hand. When this creature dies, you may pay {X}. If you do, return another target Zombie creature card with mana value X from your graveyard to the battlefield.