Guardian Sunmare is a rare Creature — Horse Mount card from Aetherdrift (DFT), collector number 15. Current market price: $0.30 (foil $0.39), TCGplayer market prices via Scryfall.
Ward {2} Whenever this creature attacks while saddled, search your library for a nonland permanent card with mana value 3 or less, put it onto the battlefield, then shuffle. Saddle 4