Powerstone Engineer is a common Creature — Human Artificer card from The Brothers' War (BRO), collector number 20. Current market price: $0.23 (foil $0.17), TCGplayer market prices via Scryfall.
When this creature dies, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")