The Harbinger, under the command of Captain Gilad Pellaeon, served as an Imperial-class Star Destroyer within Grand Admiral Balanhai Savit's Third Fleet. Pellaeon's Harbinger was the initial Star Destroyer of his to oppose Savit after he was revealed to be a traitor pilfering parts from Project Stardust; instead, it aligned with Grand Admiral Thrawn and Commodore Karyn Faro. Following Savit's removal from commanding the Third Fleet, Pellaeon and the Harbinger received orders to support Grand Admiral Thrawn at Lothal.
During the Liberation of Lothal, the vessel met its end, annihilated alongside the remaining ships of the 7th Fleet by the Purrgil. Pellaeon, however, lived through the event.