During the Galactic Civil War, the New Republic embarked on a mission within the Spawn Nebula. The purpose was to investigate and neutralize the Kaarenth Dissension operating in the Corva sector.
Shortly after the conclusion of the Thrawn campaign, a team from the New Republic was sent to investigate the increasing presence of the Kaarenth Dissension within the Corva sector. On the planet of Betha II, the agents identified Meres Ulcane as the leading figure of the Kaarenth Dissension in that region.
Using the experimental Drooim-Durtha Systems ShipFinder technology, the New Republic team successfully tracked Ulcane's ship from Betha II to his hidden base, located within the Spawn Nebula. The Kaarenth Dissension's base turned out to be an enormous worldcraft, transformed into a repair and shipyard center. Furthermore, the New Republic agents discovered that the worldcraft was surrounded by a complete fleet of warships, which included assault shuttles, system patrol crafts, frigates, Strike-class medium cruisers and even an Imperial-class Star Destroyer. This secret fleet, currently unmanned, had been assembled over the past year with the intention of attacking the New Republic at some point. By following a freighter en route to the space station, they managed to land their ship, the Instigator, inside one of the sphere's hangars. The New Republic operatives successfully infiltrated the worldcraft and even gained access to the main reactor area, where they planted explosive charges, specifically illerium. However, the agents were eventually discovered and engaged by stormtroopers. They quickly retreated to the hangar and escaped in their starship. Once in space, they were attacked by eight TIE fighters, but the Instigator destroyed all of them. An Interdictor cruiser later arrived in the area but it was too late to prevent the New Republic ship from entering hyperspace. At that precise moment, the explosives detonated within the worldcraft. The resulting explosion destroyed the massive sphere, and the shock wave obliterated the nearby starships.
The destruction of the Kaarenth Dissension fleet in the Spawn Nebula effectively eliminated the Imperial faction's chances of overthrowing the New Republic in the Corva sector. The death of Meres Ulcane, as well as the loss of the majority of his fleet, was a significant blow to the Dissension. However, the use of illerium to destroy the worldcraft ultimately inspired Ennix Devian, the leader of the Kaarenth Dissension, in his subsequent attack against the New Republic.