Vanquisher's Banner is a rare Artifact card from Ixalan Promos (PXLN), collector number 251p. Current market price: $5.34 (foil $24.50), TCGplayer market prices via Scryfall.
As this artifact enters, choose a creature type. Creatures you control of the chosen type get +1/+1. Whenever you cast a creature spell of the chosen type, draw a card.