Horn of the Mark is a rare Legendary Artifact card from Tales of Middle-earth Promos (PLTR), collector number 241s. Current market price: — (foil $3.22), TCGplayer market prices via Scryfall.
Whenever two or more creatures you control attack a player, look at the top five cards of your library. You may reveal a creature card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.