Herald's Horn is a uncommon Artifact card from Warhammer 40,000 Commander (40K), collector number 241★. Current market price: — (foil $10.18), TCGplayer market prices via Scryfall.
As this artifact enters, choose a creature type. Creature spells you cast of the chosen type cost {1} less to cast. At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.