Aiya Eärendil Elenion Ancalima!
Also known as the Star-Glass, the Phial was Galadriel’s parting gift to Frodo Baggins upon the Fellowship’s departure from Lórien, which he later used to escape from Shelob’s Lair. It was made from crystal and held a fragment of the light of the evening star (Eärendil), suspended in the water from Galadriel’s fountain.
Frodo and Sam both used the Phial while traveling through Cirith Ungol to fend off attacks from Shelob. Sam also used it to overcome the will of the Two Watchers at the Tower of Cirith Ungol. However, once they reached Mount Doom, the light faded from the glass, as its power could not reach into the heart of Sauron's domain.
Frodo took the Phial with him into the Undying Lands; its light faded away as the ship approached the shores of Eldamar.