During the Great Hyperspace War, the Sith Empire's forces and the unified Koros system's army engaged in a significant conflict. In 5000 BBY, Naga Sadow, the Dark Lord of the Sith, marshaled an invasion force and initiated an assault on the Galactic Republic. Sadow's Sith apprentice, Gav Daragon, a native of Koros Major, led a portion of the Sith fleet to seize the Koros system, executing a two-pronged offensive aimed at both his homeworld and the planet Kirrek. Despite having a reduced fleet because of a recent war, the Koros military, under the command of Empress Teta and Vontaige, a top advisor and general, were confident in their ability to put up a strong defense. During the ground battle on Koros Major, Gav Daragon utilized a dropship to reach the primary combat zone in the city of Cinnagar in search of his long-lost sister, Jori. While looking for her, accompanied by his company of Massassi guards, Daragon encountered Aarrba, a former Hutt acquaintance, resulting in the Hutt's death. Jori Daragon arrived at that moment and confronted her brother about the Hutt's death. Overwhelmed by emotion, Gav abandoned the battle and fled, resolving to attack Sadow and bring the war to an end. The Sith were defeated because Gav Daragon was no longer there to lead them.
In the year 5000 BBY, Jori Daragon, a hyperspace explorer, made her way back to Koros Major, her home planet, following her escape from the long isolated Sith Empire. Jori, after sneaking into the palace of Koros system's leader, Empress Teta, alerted the Empress to the Sith's preparations for an expansionist war against the Galactic Republic. Shortly thereafter, a significant portion of Dark Lord of the Sith Naga Sadow's force, commanded by Sith apprentice Gav Daragon, Jori's brother, assembled within the Koros system. A gathering took place in Teta's palace, where the Empress selected Vontaige, one of her foremost advisors and generals, to assist in leading her forces in the defense of Koros Major against the Sith. Despite the fact that many of the fleet's warships had suffered destruction or damage in the recent Koros Unification Wars, Teta remained optimistic that they could still put up a good defense. The inhabitants of Koros Major resolved to defend their world at all costs and launched their battleships. The Koros military began to establish defensive positions inside the capital city of Cinnagar, and Teta herself began preparing for battle, donning a heavy suit of battle armor and wielding a large lance. Jori Daragon also equipped herself with a protosaber that had been gifted to her by Jedi Knight Odan-Urr.
The Sith fleet immediately initiated a bombardment of the planet, triggering panic among Cinnagar's civilian population. Numerous dropships, carrying Sith Massassi warriors and war behemoths, were deployed towards the planet's surface. The Koros military deployed anti-aircraft guns as a countermeasure against the approaching ships. These shots were often erratic during the onslaught, and some nearly struck residential homes and businesses. Meanwhile, Gav Daragon, disregarding the objections of his subordinates, chose to descend to the surface of Koros Major in a dropship, accompanied by a contingent of Massassi guards. Gav informed them of his intention to attempt a shutdown of the city's defenses to facilitate a near-bloodless victory. However, he harbored an ulterior motive: he sought information regarding the whereabouts of his sister, Jori. He landed near the repair dock of Aarrba, a Hutt who was an old acquaintance of the Daragon family. However, when Gav inquired about his sister's location, the Hutt simply spat in his face. Interpreting this as an act of aggression, Gav's Massassi guards stabbed the Hutt in his abdomen. Mortally wounded, the Hutt fell from his hoversled and crushed the Massassi guards to death.
Jori Daragon arrived on the scene at that moment and spotted the dead body of Aarrba. Blaming her brother for the Hutt's death, Jori became enraged and slew the lone remaining Massassi guard with her activated lightsaber. With tears in her eyes, she confronted Gav about Aarrba's death. Overcome with the emotion of the situation, Gav Daragon fled the scene. He returned to his flagship and abandoned the battlefield of Koros Major to confront Naga Sadow, hoping to end the war that had ravaged his home and driven him and his sister apart. Without their commander, the Sith force was defeated by Teta and the Koros military.
Jori Daragon subsequently led Teta's fleet in pursuit of her brother Gav, who had found himself in a predicament: he had become trapped aboard Sadow's empty Sith Meditation Sphere after Sadow tricked him into coming aboard the vessel by promising to meet him face-to-face. Gav gave the Koros forces the location of the Sith Empire, but soon afterward, Sadow reappeared and triggered a secret weapon to destroy the nearby star of Primus Goluud. The ensuing explosion killed Gav Daragon. Sadow returned to the Sith Empire defeated; his forces had taken losses at Koros Major, Coruscant, and Kirrek, thereby ending any hope of a victory for the Sith Empire. Teta's forces followed him to the Empire's holdings and defeated him in battle over Korriban, forcing the Dark Lord of the Sith to fake his death and flee to the faraway moon of Yavin 4. The city of Cinnagar was greatly damaged in the battle, but it had been fully rebuilt by 3996 BBY and was flourishing at that time.
The battle on Koros Major is an event that first appeared in Tales of the Jedi: The Fall of the Sith Empire, a story arc of the comic book series Tales of the Jedi, written by Kevin J. Anderson and released in 1997. The lead-up to the battle and much of the action is featured in the arc's third issue, First Encounter, with closure to the Daragons' saga during the battle being given in the fourth issue, The Dogs of War. In these appearances, the battle is illustrated by Dario Carrasco, Jr.