Rakdos, Lord of Riots is a mythic Legendary Creature — Demon card from Duskmourn: House of Horror Commander (DSC), collector number 230. Current market price: $2.53, TCGplayer market prices via Scryfall.
You can't cast Rakdos unless an opponent lost life this turn. Flying, trample Creature spells you cast cost {1} less to cast for each 1 life your opponents have lost this turn.