A crystal phial given to Frodo by Galadriel in Lothlorien, containing the light of Earendil's star - itself the light of one of the Silmarils, which captured the radiance of the Two Trees of Valinor. It shines in dark places and is a bane to creatures of evil. Frodo and Sam use it to pass the Watchers at Cirith Ungol, and Sam wields it against Shelob in the tunnels above Minas Morgul.