The Dämmerung is the headquarters of Vector Industries and a massive colony that harbors the Vector Corporation's primary buildings. Vector's First, Second, and Third R&D Divisions are headquartered on the Dämmerung. At the very top of the pyramid-like structure in the centre of the ship is Wilhelm's private office, where the Compass of Order is located. At 1,000 km long, it is so large that it could be considered an artificial planet. It carries on it the Rhine Maiden, a devastating large-scale anti-Gnosis weapon and millions of photon torpedo tubes.
While only glimpsed in Episode I, the Dämmerung serves as one of Episode II's playable areas. Shion, with Allen in tow has to navigate a maze of passageways, factories, and warehouses within the bowels of the Dämmerung in order to find E.S. Dinah and fly to Old Miltia. The Dämmerung plays a somewhat minor role in Episode III, appearing sparsely throughout the game and for the most part near the end. After the planetary disappearance phenomenon and the destruction of the U.M.N. at the end of the game, the Dämmerung becomes one of last (possibly the only) remaining centres of civilization in the Xenosaga universe. All the surviving party members and major characters end up on the Dämmerung in the ending, though Shion, Allen, Jr., Mary, Shelly and the Elsa crew depart on a mission to find Lost Jerusalem.
In Xenosaga I&II the Dämmerung was shown hovering curiously close to the surface of Second Miltia. In the scene, Shion takes Allen to a hillside overlooking the city and she tells him that she used to go there and look up at the stars to forget her troubles. She appears to be passively referring to how the Dämmerung is blocking out much of the sky from orbit.
Dämmerung is German and means twilight in English. The name is most likely derived from Götzen-Dämmerung, a philosophy book by Friedrich Nietzsche. Götzen-Dämmerung means "Twilight of Idols" and itself is a pun derived from the opera Götterdämmerung ("Twilight of Gods") by composer Richard Wagner, a close friend of Nietzsche. In Norse Mythology, Gotterdammerung is another name for Ragnarok, the end of the Earth. At this time, the Gods engage in a final conflict with various opposing forces of evil, and the entire world will be destroyed by fire, sinking into the sea to rise again as an ideal world full of only goodness, where Gods and men live together in harmony. This can be seen as a rather ironic naming, as Wilhelm's objective is preventing the end of the world through repeating history over and over again.
Several early technical demo screenshots released for Episode I showed Shion exploring Wilhelm's pyramid-like office. In all three Xenosaga games, however, Shion never visits Wilhelm's office. Only two characters ever appear in that location, Kevin Winnicot as the Red Testament and Wilhelm himself. However in Xenosaga: The Animation Kevin is joined by Virgil and Voyager, the blue and black Testaments, respectively.