Cultist of the Absolute is a rare Legendary Enchantment — Background card from Battle for Baldur's Gate Promos (PCLB), collector number 123s. Current market price: — (foil $8.10), TCGplayer market prices via Scryfall.
Commander creatures you own get +3/+3 and have flying, deathtouch, "Ward—Pay 3 life," and "At the beginning of your upkeep, sacrifice a creature."