Street Spasm is a uncommon Instant card from Duel Decks: Izzet vs. Golgari (DDJ), collector number 30. Current market price: $0.26, TCGplayer market prices via Scryfall.
Street Spasm deals X damage to target creature without flying you don't control. Overload {X}{X}{R}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")