Great Desert Prospector is a uncommon Creature — Human Artificer card from The Brothers' War (BRO), collector number 7. Current market price: $0.17 (foil $0.23), TCGplayer market prices via Scryfall.
When this creature enters, create a tapped Powerstone token for each other creature you control. (They're artifacts with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")