Thassa's Rebuff is a uncommon Instant card from Born of the Gods (BNG), collector number 54. Current market price: $0.37 (foil $0.82), TCGplayer market prices via Scryfall.
Counter target spell unless its controller pays {X}, where X is your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)