Soul Immolation is a mythic Sorcery card from Lorwyn Eclipsed (ECL), collector number 321. Current market price: $3.70 (foil $5.94), 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.