Street Spasm is a uncommon Instant card from Return to Ravnica (RTR), collector number 106. Current market price: $0.15 (foil $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.")