Counterflux is a rare Instant card from Return to Ravnica (RTR), collector number 153. Current market price: $0.43 (foil $3.24), TCGplayer market prices via Scryfall.
This spell can't be countered. Counter target spell you don't control. Overload {1}{U}{U}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")