In Tolkien's fictional universe of Middle-earth, the Phial of Galadriel was the parting gift to Frodo Baggins by Galadriel when the Fellowship of the Ring left Lórien.
It was also known as the Star-glass, because it held a little fragment of the light of the Evening Star Eärendil, which was one of the Silmarils, contained within the waters of Galadriel's Mirror.
While travelling to Mordor via Cirith Ungol, both Frodo and Samwise Gamgee used the light of the Phial to fend off attacks from the monstrous arachnid Shelob in Torech Ungol. Sam also used it to overcome the will of the Two Watchers at the Tower of Cirith Ungol. Once they reached Mount Doom, however, the light from the glass faded because they were in the heart of Sauron's domain where its power could not reach.
Frodo took the Phial with him when he left Middle-earth for the Undying Lands. Its light faded away as the ship approached the shores of Eldamar.
full article at wikipedia
