Vivien's Arkbow is a rare Legendary Artifact card from War of the Spark (WAR), collector number 181. Current market price: $0.30 (foil $0.45), TCGplayer market prices via Scryfall.
{X}, {T}, Discard a card: Look at the top X cards of your library. You may put a creature card with mana value X or less from among them onto the battlefield. Put the rest on the bottom of your library in a random order.