In the year 3640 BBY, amidst the Galactic War between the Galactic Republic and the Sith Empire, the Republic Navy, in conjunction with the Jedi Order, executed a clandestine undertaking known as the Dromund Kaas operation. This operation involved an assault on Dromund Kaas, the Imperial capital planet. While Grand Master Satele Shan of the Jedi led the naval forces in a diversionary engagement against the Imperial First Defense Fleet, a specialized team, spearheaded by the Jedi Knight celebrated as the Hero of Tython, secretly infiltrated Dromund Kaas. Their objective was to confront the Sith Emperor himself, whose recent attempts at massacre on Belsavis, Voss, and Corellia were viewed as sacrifices needed to initiate a dark side ritual to consume all life in the galaxy. The Jedi hoped to eliminate the Emperor before he could finalize these devastating plans.
The Hero, accompanied by a small band of allies, battled through the Imperial capital of Kaas City, eventually commandeering the Sith Emperor's shuttle to fly to the nearby Dark Temple. Within the temple, they fought past the Imperial Guardsmen and Sith who guarded the Emperor. While the Hero's companions engaged these defenders, the Knight, along with the astromech droid T7-O1, confronted the Emperor in the temple's core. The Knight struck down the Emperor in combat, though only the host body housing the Emperor's immortal essence was destroyed. Nevertheless, the Jedi and much of the galaxy believed the Emperor to be truly dead. Following this, Darth Malgus, a Sith Lord known for his disagreements with Imperial policies, seized the Emperor's Fortress and proclaimed a New Empire, while the six powerful Sith known as the Dread Masters sought to dominate the galaxy themselves. Despite widespread rumors of the Emperor's demise, both the Empire and the Republic officially concealed his death until after the invasion of Makeb two years later, when Leontyne Saresh, the Supreme Chancellor of the Republic, publicly revealed the success of the previously classified operation.
In the distant past of 4999 BBY, the Sith Lord known as Vitiate employed a ritual rooted in Sith magic to drain the life from every being on his homeworld of Nathema. This casting removed the Force itself from the entire planet, killing all living things on Nathema. Vitiate then absorbed their collective life force, which dramatically increased his strength in the Force and granted him immortality. Becoming the Sith Emperor, he then reconstituted the Sith Empire and ruled it for over a thousand years. Over this extended time, the Emperor continued to explore Sith magic, seeking methods to amplify his power even further.
In 3950 BBY, the Emperor faced an attack from three powerful Force users: the Jedi Revan and Meetra Surik, and the Sith Lord Scourge. They nearly succeeded in defeating him. However, during the confrontation, Scourge experienced a vision of the future, revealing another Jedi standing victorious over the Emperor. Understanding the Emperor's threat to the galaxy, Scourge chose to betray Revan and Surik to ensure this future would occur.
Consequently, Scourge was named the Emperor's Wrath, the Emperor's personal enforcer, and served him for the next several centuries. Surik was killed, and Revan was captured and tortured during this same period. As a result of his near-death experience, the Emperor sought a method to transfer his consciousness and powers between host bodies, which he then used to protect his true body from harm. Among Imperials, the host body became known as the Emperor's Voice.
In 3641 BBY, the Galactic War began between the Empire and the Republic, largely because the Republic had freed Revan. During his imprisonment, Revan had used the mental link between himself and the Emperor to weaken the Emperor's desire to annihilate the galaxy. As the war erupted, the Emperor began planning to replicate his ritual on a galactic scale, aiming to consume the entire galaxy as he had Nathema. Approximately one year later, he dispatched several Sith and Dark Jedi agents to various planets to orchestrate mass deaths, providing the necessary sacrifices to begin his ritual. However, Scourge betrayed the Emperor and sought out the Jedi from his vision, a Jedi Knight known as the Hero of Tython.
Scourge informed the Jedi Council about the Emperor's schemes and allied with the Hero to prevent the ritual. With Scourge's assistance, the Hero thwarted the Emperor's plans on Belsavis, Voss, and Corellia. On Corellia, the Emperor's agent, the Dark Jedi Tol Braga, provided the Hero with the Emperor's coordinates on the Imperial capital world of Dromund Kaas. With the Emperor's location secured, Grand Master Satele Shan of the Jedi Order determined that the moment was right to strike against the Emperor before he could complete the sacrifices required for his ritual. Consequently, she assembled a joint task force of Republic Navy and Jedi warships to assault Dromund Kaas, tasking the Hero and their crew of allies with infiltrating the capital and eliminating the Emperor.
Upon their arrival in the Dromund system, the Republic task force immediately engaged the Imperial First Defense Fleet, drawing the bulk of the Imperial forces in the system into the battle. Under the cover of this engagement, the Hero's crew slipped into Imperial airspace and landed their Defender-class light corvette on the outskirts of Kaas City. The Hero's team consisted of six individuals: the Hero, Lord Scourge, Jedi Knight Kira Carsen, the combat medic Archiban Kimble, the Republic trooper Fideltin Rusk, and the astromech droid T7-O1. Utilizing Scourge's knowledge of the city, the group concluded that the most direct path to the Emperor, who was located in the Dark Temple in the nearby jungle, involved stealing one of the Emperor's personal shuttles docked within the city.
The team divided into three pairs and fought through Kaas City, which was lightly defended by Imperial soldiers, Imperial commandos, Mandalorian mercenaries, and war droids, including a massive Imperial Ravager Droid. All three pairs successfully reached the shuttle, where they finalized their strategy before proceeding. Given the Emperor's immense power, none of the others could safely accompany the Hero into battle without risking control; however, because T7-O1 was a droid, it could face the Emperor without being vulnerable to manipulation. The remaining four would engage the temple's defenders to divert opposition from the Hero and T7-O1, clearing their path to the Emperor. Scourge flew the shuttle to the Dark Temple, where the six stormed the edifice, battling dozens of Imperial Guardsmen and Sith assassins guarding both the temple and their Emperor.
Despite the enemy's superior numbers, the Hero and T7-O1 quickly reached the stairs leading to the upper levels, where the Emperor awaited. However, as T7-O1 interfaced with the temple security system and disabled the force field blocking the stairwell, it detected that one of the Hero's companions was about to be overwhelmed by Imperial Guard reinforcements nearby. Unwilling to allow a companion to die for the mission, the pair rushed to their ally's aid, eliminating the numerous Imperial Guards and rescuing their companion before returning to the stairwell and continuing toward the Emperor. Confident in his power, the Emperor awaited the Hero's arrival in one of the temple's upper chambers, unconcerned when the Jedi and T7-O1 breached his sanctum.
The Sith greeted his foe with a blast of violet Force lightning, mocking the Hero for sacrificing strength to save an ally. The Hero intercepted the lightning with their lightsaber, and the Emperor summoned three phantom duplicates of himself to attack the Knight and droid as he descended from his throne to engage his enemy. The pair swiftly defeated the phantom opponents, and when the Hero questioned the Emperor's desire to consume the galaxy, the Emperor dismissed the Jedi's limited understanding of his ambition—he intended to outlast everything, with more galaxies and universes to conquer beyond their own.
The Sith then summoned more duplicates of himself and drew his own lightsaber, and the numerous Emperors attacked their opponents. The Emperor and his copies used Force lightning, Sith magic, and lightsabers in battle, disappearing and reappearing throughout the chamber to confuse the Jedi. However, the Hero and T7-O1 stood strong, and one by one, the Emperor's duplicates vanished in swirls of dark side energy until the true Emperor fell to his knees. The Hero charged the Emperor, intending to end the battle, but the Sith unleashed an explosive blast of Force lightning that threw his enemy across the room. Acknowledging the Hero's strength in the Force, the Emperor cast another burst of Force lightning directly at the Jedi, only for them to catch the attack on their lightsaber blade.
As the Emperor continued to generate lightning, the two enemies advanced on each other, but when they met, the Hero dodged the lightning and dealt the Emperor a devastating blow to his waist. The Sith ruler collapsed. As he tried and failed to rise, he declared that he would never be contained or redeemed, scoffing at the Hero's claims that he would be taken to Tython and turned from the dark side. The Hero then contacted Scourge and reported success, but Scourge warned that the Emperor was not yet dead.
Scourge was correct. The Emperor's essence left his fallen Voice and, warning the Hero that he would take his enemy with him in death, released a massive burst of dark side energy from the Voice as a final act of defiance. The released energy severely damaged the Dark Temple, causing the upper levels to collapse, and the Hero and T7-O1 rushed out of the temple to safety. The pair reunited with the other members of their team, all of whom had survived their battle with the temple's defenders, and flew the Emperor's shuttle back to Kaas City, boarding their own waiting ship outside the capital. Upon liftoff, the Hero contacted the Grand Master and reported the mission's success, leading Shan to order a general retreat from the Dromund system.
The remaining ships of the task force gathered at the Republic cruiser Valiant near the Core Worlds, where Admiral Dabrin of the Republic Navy and the Grand Master organized an award ceremony for the Hero and the crew. Each member received the Cross of Glory, the Republic's highest honor, and Shan promoted the Hero to the rank of Jedi Master.
With the loss of his Voice, the Emperor's essence retreated to his true body, where he entered restorative hibernation to recover from the battle. Rumors of the Emperor's death spread among the upper echelons of the Sith Empire, leading Darth Malgus, a maverick Sith Lord already disillusioned with the Empire's anti-alien policies and the infighting within the Dark Council, to rebel at the Battle of Ilum shortly thereafter. Seizing the Emperor's abandoned space fortress, Malgus declared a New Empire, dividing the Empire as many defected to his cause.
The Republic and the Empire jointly crushed the New Empire at the Battle of Ilum, but the damage was done. Combined with the recent loss at the Battle of Corellia, the Empire, which had previously held the advantage in the Galactic War, was gradually forced into a defensive position. Darth Marr, a veteran Dark Councilor, eventually assumed a leadership role and worked to restore Imperial dominance. However, it wasn't until around 3638 BBY, after the Hutt Cartel's failed invasion of Makeb, that Marr halted the Empire's decline by acquiring the powerful mineral known as isotope-5.
The details of the Dromund Kaas operation, as it became known, were highly classified by the Republic. Leontyne Saresh, the newly elected Supreme Chancellor, initially refrained from publicly announcing the operation. However, she immediately adopted an aggressive stance against the Empire, appointing the veteran soldier Jace Malcom as Supreme Commander of the Republic Military to take the fight to the Empire. A joint committee of Jedi and agents from the Republic Strategic Information Service, the Republic's intelligence agency, was tasked with confirming the Emperor's death.
As the Emperor's Hand, his most trusted servants, were responsible for guarding his body, only they and the new Emperor's Wrath knew of his survival. Thus, the committee concluded that the Emperor was indeed dead. Following the Republic's victory over the Hutt Cartel at Makeb, the Chancellor, Shan, and Malcom officially announced the Emperor's death on the HoloNet.
The battle with the Hero severely injured the Emperor's essence, forcing him into hibernation in his original body. While he slumbered, his consciousness reached out to his Children, agents mentally linked to him. His pain and anger caused him to issue crazed and conflicting commands, such as "freeze the oceans of Manaan" and "set fire to Ord Mantell," demanding the destruction of entire worlds. Unable to withstand his influence, many Children were driven insane, while others managed to block his commands, shielding themselves until he healed.
The Emperor's apparent death and subsequent hibernation had another significant impact on the galaxy: the six Sith Lords known as the Dread Masters, who had served the Emperor for centuries, were left without his guidance. Incredibly powerful in the Force, they found no one in the Empire worthy of their loyalty and decided to take control of the galaxy themselves. Wielding their power over fear and minds, the Dread Masters gathered an army and acquired exotic technology from species like the Rakata and the Gree, becoming a third power in the Galactic War. Their attacks on Hutt Space led the Hutt Cartel to expand their borders to compensate for lost territory, resulting in the death of the Cartel's Supreme Mogul, Karagga.
Toborro the Hutt succeeded Karagga as Supreme Mogul and instigated the Hutt invasion of Makeb in 3638 BBY. Shortly thereafter, the remaining Dread Masters descended into madness and sought to destroy the galaxy, though they were ultimately defeated at the moon of Oricon. In the depths of Wild Space, the Sith Emperor's biological daughter, Vaylin, discovered that the mental barriers her father had placed in her mind to suppress her full power were gone. With this realization, Vaylin began plotting her revenge against her father. The Emperor's spirit continued to play a major role in galactic conflicts, although it was not until 3626 BBY that it was finally vanquished for good.
The "Doomsday" mission, which is the climactic finale for the Jedi Knight class in Star Wars: The Old Republic, a massively multiplayer online role-playing game launched by BioWare in December of 2011, centers around the Dromund Kaas operation. However, the Dromund Kaas operation was first seen in a vision experienced by Lord Scourge in The Old Republic: Revan, a prequel novel penned by Drew Karpyshyn and released on November 15 of 2011. The droid RL-4 refers to the mission as the "Dromund Kaas operation" when he introduces the Karagga's Palace Operation for Republic players. Furthermore, Chancellor Saresh's formal declaration of the Emperor's demise is included in The Old Republic's Digital Expansion Rise of the Hutt Cartel.
During the "Doomsday" mission, the player must decide whether to save a comrade in danger, which earns them light side alignment points, or to proceed to battle the Emperor, which prevents him from gaining more power and earns them dark side alignment points. The companion in peril will be the one with whom the player has the most Affection points, with the exceptions of Lord Scourge and T7-O1. Regardless of the player's choice, the battle with the Emperor remains equally challenging. If the player opts not to save the companion, one of the player's other companions will rescue the character. At the subsequent award ceremony, the player will be granted either the title of Jedi Master or general, depending on whether their alignment score is light or dark, respectively. Given that the Jedi Knight is a Republic-aligned class, this analysis presumes that the player selects the option that yields the most light side points; consequently, it is assumed that the Hero of Tython saved the companion and was promoted to Jedi Master.