Flusterstorm is a rare Instant card from Mystery Booster 2 (MB2), collector number 163. Current market price: $4.88 (foil $53.50), TCGplayer market prices via Scryfall.
Counter target instant or sorcery spell unless its controller pays {1}. Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)