During the Lothal campaign, the ISD Dark Omen functioned as the commanding warship for a squadron composed of Star Destroyers belonging to Grand Admiral Thrawn's 7th Fleet. The Battle of Atollon commenced when Admiral Kassius Konstantine was instructed by Grand Admiral Thrawn to dispatch the fleet to the planet of Atollon prior to the arrival of Thrawn's ISD Chimaera. This military contingent was comprised of the five Star Destroyer squadron headed by Dark Omen, in addition to a pair of Interdictor-class heavy cruisers and also two Arquitens-class command cruisers. Before the Chimaera arrived, the forces of the 7th Fleet engaged the Rebel Alliance's naval forces positioned above Atollon. Although several rebel vessels successfully evaded capture, the Imperial forces achieved victory at the Battle of Atollon.