Argothian Opportunist is a common Creature — Human Scout card from The Brothers' War (BRO), collector number 167. Current market price: $0.06 (foil $0.10), TCGplayer market prices via Scryfall.
When this creature enters, create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")