The initial confrontation between the combined forces of the Galactic Republic and the Sith Empire with the Eternal Fleet occurred in 3636 BBY. In this year, Darth Marr spearheaded an expedition consisting of seven vessels into the depths of Wild Space. The mission's objective was to locate the former Sith Emperor, Vitiate, and to investigate the mysterious entities responsible for the recent raids on both Imperial and Republic worlds. Unknowingly, they trespassed into the territory claimed by the Eternal Empire of Zakuul. In response, Valkorion, Vitiate's other identity, dispatched the Eternal Fleet to intercept the intruders. This formidable armada materialized from hyperspace directly above Darth Marr's group, unleashing a barrage of fire while simultaneously deploying boarding pods filled with skytroopers. Darth Marr commanded his vessels to raise shields and attempt an escape. However, a significant number of boarders infiltrated the ships, overwhelming the Imperial and Republic soldiers and causing critical system failures. Ultimately, despite Darth Marr and his ally's success in eliminating numerous skytroopers, Darth Marr's flagship sustained irreparable damage and was destroyed. Marr and his ally were taken as prisoners, although some soldiers managed to escape via escape pods, which the Eternal Fleet ignored.
During the Revanite crisis of 3637 BBY, certain individuals within the reconstituted Sith Empire and the Galactic Republic came to the realization that Vitiate, the former Sith Emperor, presented a considerably greater threat than the ongoing Galactic War because of his apparent intention to devour all life in the galaxy. Satele Shan, the Jedi Grand Master, and Darth Marr, a member of the Dark Council, established the Yavin Coalition by uniting their forces. Despite their efforts, they failed to prevent Revan from reviving the Emperor's spirit on Yavin 4. Upon awakening, Vitiate fled to Ziost, where he employed his ritual to consume all life on the planet. Subsequently, his spirit escaped into Wild Space.
Shortly thereafter, a mysterious army, commanded by twin conquerors, launched a series of raids targeting both Republic and Imperial worlds. This included an attack on Korriban that left the Sith Academy and the Valley of the Dark Lords devastated. Many Sith were either killed or forced into servitude by the conquerors. This army, unchallenged and undefeated, retreated into Wild Space before their true identity could be discovered. They were the Eternal Empire of Zakuul, another creation of Vitiate that he had secretly developed in the Unknown Regions over centuries, under the guise of Valkorion. To pursue these adversaries, Darth Marr, who had become the de facto leader of the Sith Empire following Vitiate's abandonment, assembled a joint task force comprising Imperial and Republic personnel. This force primarily consisted of veterans from Yavin 4 who had witnessed Vitiate's power firsthand. Their mission was to venture into the uncharted territories of Wild Space. Unbeknownst to them, Marr's task force was about to cross into the borders of the Eternal Empire. In response, Valkorion, known as the Immortal Emperor on Zakuul, dispatched his Eternal Fleet to confront the intruders.
Darth Marr was leading the expedition from his flagship when a small vessel emerged from hyperspace and docked with it. This vessel belonged to an ally Marr had gained during the Revanite crisis. Captain Fora greeted her guest and escorted them to the bridge. There, Marr confirmed that he sensed the Emperor's presence growing stronger and questioned the significance of the Republic's contribution. Suddenly, a small probe appeared near the vessel, and Marr ordered the activation of deflector shields and the destruction of the probe to prevent it from revealing their position. However, before the order could be executed, the massive Eternal Fleet, previously unknown to the galaxy, emerged from hyperspace and commenced firing.
Marr immediately commanded evasive maneuvers to move the ship out of the direct line of fire. However, the Eternal Fleet launched boarding pods that penetrated the flagship's hull on every deck, deploying skytrooper droid soldiers. Republic and Imperial soldiers fought side by side against the unknown invaders, who possessed superior numbers. Marr's ally hurried to clear the boarders, driving them from the starboard compartment and stopping their assault on the shield generator, even though they continued to spread elsewhere on the ship. A group of Republic soldiers found themselves trapped behind a blast door, which Imperial Sergeant Dol ordered to be sealed to halt the invaders. Corporal Ralo of the Republic refused to abandon his comrades. Darth Marr's ally agreed to handle the enemy droids in that area, allowing the Republic troopers to retreat and regroup. Marr's ally then rushed to eliminate hostiles in the port section, where enemy fire had destroyed the airlock and fused the docking clamps on their ship, preventing their crew from joining or leaving.
Fighting through skytroopers, Marr's ally hastened to the airlock and disengaged the docking mechanisms, allowing their ship to break free. Their crew then piloted it away from Marr's flagship. By this point, the enemy had breached the engineering deck, attempting to disable the primary power generator. With the bridge temporarily secure, Darth Marr personally cut through the enemy droids and rushed to the generator alongside his ally. However, enemy firepower had penetrated the flagship's shields and struck the main thrusters. By the time Marr and his ally reached the power core, it was strained to its breaking point. The defensive barricades on the bridge had fallen, and in an attempt to save as many lives as possible, Marr's ally ordered the remaining personnel to evacuate in the escape pods. Some soldiers, including Corporal Ralo, escaped before the concentrated fire from the Eternal Fleet destroyed Marr's flagship, with all other vessels already out of the picture.
Despite the vessel's destruction, Darth Marr and his ally survived and were captured by the Eternal Empire while unconscious. The Empire also recovered various records from the wreckage's ship computers. Marr and the other prisoner were transferred to the Eternal Flagship of Prince Arcann, who transported them to Zakuul and presented them to his father. During the ensuing confrontation, Valkorion killed Darth Marr but was then betrayed by his son, resulting in the death of his physical form. However, his spirit, as always, endured. Survivors from the battle, using the multiple escape pods, carried the news back to the Empire and the Republic. Soon after, the Eternal Empire, now under the leadership of Emperor Arcann following his father's death, launched a full-scale invasion. The galaxy then witnessed the full destructive power of the Eternal Fleet during the subsequent Eternal Empire conquest.
Chapter I: The Hunt marks the beginning of the Knights of the Fallen Empire storyline. Players of any class can participate, starting with their unique ship and the original five class companions. However, by the end, they are all merged into "The Outlander" character. The player also briefly gains Darth Marr as a companion, but this lasts only a short time, as Marr is killed by the chapter's conclusion. Players face several choices during the battle, the first being whether to allow Sergeant Dol to seal the blast door, trapping the Republic troopers behind it. In the Light Side option, the player volunteers to handle enemy forces, earning the approval of Corporal Ralo. In the Dark Side option, the player agrees with Dol, leading to Ralo's disapproval. After freeing their ship, players can order their companions to escape and deliver news to civilization or stay and engage the Eternal Fleet to buy time for themselves and Darth Marr. Regardless, the player's companions escape the battle, and no mention is made of the player's choice upon their return. Finally, players can order the flagship's evacuation in a Light Side choice or ram it into the Eternal Fleet as a Dark Side choice, destroying several Eternal Fleet warships but reducing the number of survivors. Ralo will remember this choice and address it during Chapter VI: Asylum.