Swift Warden is a uncommon Creature — Merfolk Warrior card from Rivals of Ixalan (RIX), collector number 146. Current market price: $0.17 (foil $0.47), TCGplayer market prices via Scryfall.
Flash When this creature enters, target Merfolk you control gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)