Ob Nixilis, Unshackled is a rare Legendary Creature — Demon card from Magic 2015 (M15), collector number 110. Current market price: $3.99 (foil $7.54), TCGplayer market prices via Scryfall.
Flying, trample Whenever an opponent searches their library, that player sacrifices a creature of their choice and loses 10 life. Whenever another creature dies, put a +1/+1 counter on Ob Nixilis.