Hall of Tagsin is a rare Land card from The Brothers' War Promos (PBRO), collector number 263s. Current market price: — (foil $0.41), TCGplayer market prices via Scryfall.
{T}: Add {C}. {1}, {T}: Add one mana of any color. {4}, {T}: Create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")