Norn's Annex is a rare Artifact card from New Phyrexia (NPH), collector number 17. Current market price: $5.85 (foil $22.34), TCGplayer market prices via Scryfall.
({W/P} can be paid with either {W} or 2 life.) Creatures can't attack you or planeswalkers you control unless their controller pays {W/P} for each of those creatures.