Slagstone Refinery is a uncommon Artifact card from The Brothers' War (BRO), collector number 243. Current market price: $0.19 (foil $0.33), TCGplayer market prices via Scryfall.
Whenever this artifact or another nontoken artifact you control is put into a graveyard from the battlefield or is put into exile from the battlefield, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")