Aven Liberator is a common Creature — Bird Soldier card from Scourge (SCG), collector number 4. Current market price: $0.04 (foil $0.61), TCGplayer market prices via Scryfall.
Flying Morph {3}{W} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.) When this creature is turned face up, target creature you control gains protection from the color of your choice until end of turn.