Battle at the Bridge is a rare Sorcery card from Aether Revolt (AER), collector number 53. Current market price: $0.28 (foil $0.32), TCGplayer market prices via Scryfall.
Improvise (Your artifacts can help cast this spell. Each artifact you tap after you're done activating mana abilities pays for {1}.) Target creature gets -X/-X until end of turn. You gain X life.