The Seniag was in dry dock at the Kothlis II platform near Kothlis when the Galactic Empire attacked in order to retrieve stolen plans on the Death Star II. The vessel was presumably supposed to evacuate base personnel, but never actually left the site.
Behind the scenesEdit
As aforementioned, the Seniag spends the entire level parked above Kothlis II and doesn't do anything, unlike the three GR-75 medium transports nearby that do eventually flee the site. The reason for the vessel's presence at all in the game is thus questionable.