Gauntlet of Power is a special Artifact card from Kaladesh Inventions (MPS), collector number 12. Current market price: — (foil $58.25), TCGplayer market prices via Scryfall.
As this artifact enters, choose a color. Creatures of the chosen color get +1/+1. Whenever a basic land is tapped for mana of the chosen color, its controller adds an additional one mana of that color.