Kuro, Pitlord is a rare Legendary Creature — Demon Spirit card from Duel Decks: Divine vs. Demonic (DDC), collector number 44. Current market price: $0.39, TCGplayer market prices via Scryfall.
At the beginning of your upkeep, sacrifice Kuro unless you pay {B}{B}{B}{B}. Pay 1 life: Target creature gets -1/-1 until end of turn.