Horde Ambusher is a uncommon Creature — Human Berserker card from Khans of Tarkir (KTK), collector number 110. Current market price: $0.06 (foil $0.16), TCGplayer market prices via Scryfall.
Whenever this creature blocks, it deals 1 damage to you. Morph—Reveal a red card in your hand. (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 can't block this turn.