Gray Merchant of Asphodel is a uncommon Creature — Zombie card from Theros Beyond Death (THB), collector number 355. Current market price: $7.47 (foil $10.33), TCGplayer market prices via Scryfall.
When this creature enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)