Soul Immolation is a mythic Sorcery card from Lorwyn Eclipsed Promos (PECL), collector number 156p. Current market price: $3.15 (foil $5.95), TCGplayer market prices via Scryfall.
As an additional cost to cast this spell, blight X. X can't be greater than the greatest toughness among creatures you control. (Put X -1/-1 counters on a creature you control.) Soul Immolation deals X damage to each opponent and each creature they control.