A climactic showdown unfolded between the Sith Lord Darth Vader and Galen Marek, his one-time apprentice, on the original Death Star in 2 BBY. This occurred at the commencement of the Galactic Civil War between the Empire and the Rebel Alliance. Following the capture of the Rebel founders on Corellia, the master betrayed his apprentice and left him for dead. Seeking vengeance, Marek rediscovered his Jedi heritage and pursued the Dark Lord of the Sith to the Empire's uncompleted battle station, determined to rescue his newfound allies and, by extension, the Rebellion itself.
Having penetrated the Death Star's defenses, the apprentice eliminated a multitude of stormtroopers and other Imperial soldiers before arriving at the Imperial throne room, where he faced Darth Vader in single combat. In a battle of both skill and power, Vader was eventually defeated and found himself at the mercy of his former apprentice. Vader's own master, Darth Sidious—more widely known throughout the galaxy as Emperor Palpatine—not only commended Marek's triumph but also attempted to hypnotically compel the apprentice to kill his severely wounded and defenseless master. Sidious saw in Marek the chance to replace his weakened enforcer with a younger, more potent disciple. However, Jedi General Rahm Kota, one of the prisoners seized on Corellia, detected the Emperor's schemes and tried to prevent the apprentice from succumbing to the lure of the dark side again. The distraction succeeded in breaking Sidious's control over Marek, who then confronted the Dark Lord to protect his friends. Enraged at the Jedi's attempt to claim the apprentice's potential for their own cause, Sidious tried to kill Kota with Sith lightning. Marek shielded his mentor by absorbing the energy into himself, but at the cost of his own life. To prevent a squad of stormtroopers from killing the Rebels, Marek released the power of the Force from within himself, dying as a result of the resulting explosion.
The Rebel leaders—senators-turned-fugitives Bail Prestor Organa, Garm Bel Iblis, and Mon Mothma—were evacuated from the Death Star aboard the apprentice's starship, Rogue Shadow, piloted by former Captain Juno Eclipse of the Imperial Navy. Along with Kota, the group met on Galen Marek's home planet, the Wookiee world of Kashyyyk, where they officially announced the formation of the Rebel Alliance. In recognition of their fallen leader's sacrifice, the new organization adopted Marek's family crest as their symbol; a beacon of hope for those who desired the restoration of the Galactic Republic.
Darth Sidious was far from pleased with the premature death of Darth Vader's apprentice. He was even more infuriated by the realization that the Empire would now have to wage a civil war against an insurgency secretly orchestrated by the Sith Order—specifically, Sidious and Vader, using Marek as their instrument. Forced to endure Vader's continued existence, the Emperor charged Darth Vader with the complete annihilation of the newly established Alliance, fearing that the Rebellion might dismantle the New Order that the Sith had constructed after centuries of plotting the downfall of the Jedi Order and their Republic.

In the year 2 BBY, several disillusioned members of the Imperial Senate—most notably Bail Prestor Organa from Alderaan, Garm Bel Iblis from Corellia, and Mon Mothma from Chandrila—came to the conclusion that the Galactic Empire was irredeemably corrupt and ultimately illegitimate; a perversion of the Old Republic established by Emperor Palpatine in his ambition to govern the galaxy through fear and domination. Consequently, they unanimously decided to join a growing rebellion spearheaded by a mysterious Forceful being known only as "Starkiller." The rebellious senators were unaware that their leader was the secret Sith apprentice of Darth Vader, the Dark Lord of the Sith and the Emperor's chief enforcer. The apprentice, believing that he and his Sith Master would assassinate the Emperor once he was distracted by an army of insurrectionists, gathered the Rebel leaders on Corellia where they planned to declare the formation of the Alliance to Restore the Republic.
At that moment, a heavily armed Imperial force arrived. Led by Darth Vader, a contingent of snowtroopers apprehended the senators, including Jedi Master Rahm Kota, while the Sith Lord confronted his astonished apprentice. Stunned and embittered by the revelation that his master's scheme against the Emperor had been a deception, Starkiller realized that his sole purpose in Vader's eyes was to assemble the Emperor's adversaries in one location for the Empire to capture them all at once. As Vader prepared to strike down the apprentice with his lightsaber, he was suddenly confronted by the holodroid PROXY, disguised as his former Jedi Master, Obi-Wan Kenobi. The duel was brief, and Vader left both PROXY and his former apprentice for dead.
However, Starkiller survived and was rescued by Juno Eclipse, the pilot of the Rogue Shadow. Burdened by guilt for manipulating the Rebels and motivated by resentment over Vader's treachery, the apprentice renounced his allegiance to the Sith and the dark side of the Force, declaring himself a Jedi. He reclaimed his birth name of Galen Marek, the only son of the deceased Jedi Knights Kento and Mallie Marek. In his first and last successful attempt to glimpse future events, the apprentice experienced a premonition that revealed the location of the Rebel leaders; Darth Vader had taken them to be personally executed by the Emperor on a secret battle station orbiting the prison planet Despayre in the Horuz system. Comparable in size to a small moon, the Death Star was still under construction when Marek and Eclipse arrived to rescue the senators. Fearing she might never see the apprentice again, Eclipse kissed Marek before he plunged into the Death Star's atmosphere.

Shortly after landing on the Death Star's surface, the apprentice ambushed a patrol of stormtroopers escorting a group of Wookiee slaves on the equatorial trench. With the execution of the Rebel prisoners imminent, the apprentice chose to liberate the slaves in exchange for the quickest route to the Emperor's throne room. As the Imperials were distracted by a slave uprising, a small group of Wookiees guided Marek deeper into the battlestation, toward his captive allies. Along the way, Marek single-handedly destroyed an AT-AT walker while the Wookiees fired their stolen E-11 blaster rifles at the stormtroopers who converged on the scene. As two more walkers approached, Marek ordered his allies to retreat. Three of the four Wookiees followed him; one had been killed in the firefight. Another Wookiee was fatally shot as they fell back, although the remaining two managed to regroup with the apprentice. After retreating to a safe distance, the apprentice telekinetically triggered the downed AT-AT to explode, expending all its stored munitions in a single blast. This triggered several more explosions, destroying all of the stormtroopers in the area, along with the walkers and several TIE fighters. Afterward, the two remaining Wookiees guided Marek through an accessway and brought him close to an exhaust port that would lead the apprentice where he needed to go. After thanking them for their assistance, the apprentice proceeded alone.
The apprentice soon reached the exhaust port, only to find it guarded by a full squadron of highly alert troopers, along with two laser cannons and several walkers. Using the Force to distract the soldiers, the apprentice killed both gunners before using one of the cannons to disable the nearest walker. While the guards scrambled for cover, the apprentice destroyed a second walker, and then a third one by the time reinforcements flooded the area from every direction. Before entering the exhaust port, he programmed the cannon to continue firing at random, thus covering his escape as several TIE fighters converged on its location.
As the apprentice continued toward the Emperor's throne room, he encountered several small groups of stormtroopers, all of which were dispatched with ease. After dispatching another large Imperial force stationed inside a hangar, the apprentice entered a large laser tube, which he realized was one of several components connected to the superstructure's massive laser system. With the system being test-fired every few minutes, the apprentice had to take care not to get caught in the laser beam. He also had to disable four tractor-beam reactor couplings to save Juno Eclipse and the Rogue Shadow, as she ended up caught in the Death Star's tractor beams and unable to get out of range. Upon completing this, he also eliminated a squadron of TIE fighters by throwing explosive canisters at them telekinetically before narrowly evading a superlaser beam in one of the tunnels he dived into. After several treks, he eventually ended up in a massive AT-AT hangar, where he took care of several Imperial forces, including a freshly deployed AT-ST, before continuing on. By the time he reached the top of the laser tube, he had realized the battlestation's full power. The laser he had previously observed was just one of eight tributary lasers that converged to create a beam powerful enough to destroy an entire planet. Convinced that the Death Star's only purpose was to unleash mass genocide across the galaxy, the apprentice briefly considered destroying the station on his own. He dismissed the idea, however, believing that such a task ultimately fell to the Rebel Alliance.
Before the apprentice could enter the observation deck that contained the throne room, he was forced to contend with another large number of Imperial soldiers, consisting of stormtroopers, scout troopers, jumptroopers, Purge troopers, and two AT-ST walkers. Destroying all opposition in his path, the final obstacle in his path consisted of several members of the Imperial Royal Guard, led by a single Shadow Guard. After killing all of the guardsmen, the apprentice entered the hallway leading to the throne room, preparing for the final confrontation between himself and his former master.

Just before the apprentice arrived, Palpatine informed the imprisoned Rebel Alliance leaders of his intention to execute them, but not before torturing them to extract information about any other allies and friends they might have. When Organa argued that killing them would only fuel more resistance, Palpatine dismissed him, confident that their executions (which he promised would be public and extremely painful) would crush any dissent and serve as a warning to the rest of the galaxy. Kota sensed Marek's arrival and speculated that a true rebellion might still be possible.
The apprentice entered the throne room, surprising his captured allies and the two Sith Lords. He was not deceived by the Emperor's seemingly frail appearance; he sensed the immense power of the dark side of the Force in Darth Sidious. Nevertheless, it was Darth Vader who commanded his full attention, turning his bitterness into a desire for revenge. Even as the Emperor ordered Vader to kill Marek, the Dark Lord moved to confront his former student, intending to finish what he had failed to do on Corellia.
Despite numerous sparring sessions and psychological battles in the past, Marek was surprised by the sheer intensity of his master's initial attack. The apprentice was familiar with Darth Vader's refined form of Djem So, but the Dark Lord's physical strength was so great that it jarred his wrists and shoulders, almost disarming him. However, while Vader was strong and relentless, the apprentice was fast and cunning. And there were forms of fighting that didn't involve lightsabers. Loose objects, accelerated to killing speeds by the Force, became projectiles that converged from all directions. Invisible fists clutched for throats or punched with the power of pile drivers. Floors tipped underfoot; severed beams stabbed like javelins; overloaded circuits exploded. Adopting a mostly defensive stance against his master's brutal attacks, Vader fought brilliantly, employing nothing less than killing blows. All he needed was one slip, a small breach in his opponent's defenses. Even with his skill in Soresu, Marek had to spin and dance around their Master's defenses, testing them to their limits, but he still couldn't penetrate his master's solid defenses, as his swordsmanship included elements of Soresu. Readjusting his tactics, the dark lord used sweeping moves. To disrupt their apprentice's spin, they struggled back and forth through the observation dome, realizing that he was being outmatched and that he could not resist his former master's deadly blows for much longer. Marek occasionally taunted Vader, hoping to break his concentration. At the same time, they both utilized telekinesis against one another, occasionally hurling missiles and other projectiles back and forth. For a time, neither could gain the advantage, despite their knowledge of the Force or their skills with a lightsaber.
During their duel, the apprentice couldn't help but respect his master's fighting skills. When not holding back, Darth Vader employed nothing less than a lethal attack. Marek also realized that he and Vader finally had the opportunity to test their full potential against each other, as their previous duels usually ended with Vader restraining himself or the apprentice surrendering. As the two continued to fight, Marek declared that his goal was to kill Vader, but out of pity rather than hatred. From the apprentice's perspective, he and his master had more in common than he had initially thought. Both had been made to suffer and submit to the dark side by a Sith Master. But while Marek embraced redemption as a Jedi, Vader couldn't find the will to break free from the Emperor's control. Refusing to be a slave of the Sith any longer, the apprentice vowed to free his former master by ending his life.
Vader intensified his attacks, battering at his apprentice's defenses. Marek was forced back by the barrage of blows, nearly losing his breath and close to being overwhelmed. But the apprentice counterattacked with a blast of Force lightning and broke his master's momentum. The Sith Lord responded by trying to telekinetically choke Marek, causing the apprentice to retaliate with a powerful push to the chest, sending Vader backward across the observation dome. As the duel continued, Marek steadily gained the advantage. Vader tried to retreat, but his former apprentice intensified the frequency of his attacks to keep the Dark Lord on his back foot. It was then that the apprentice saw the opening they had both been waiting for: Vader's speed was hindered too much by his own armor and prosthetic replacements. He was too slow to block an attack to the torso, allowing the apprentice's blade to slash across his armored throat.
The Dark Lord staggered backward, his gloved hand covering the wound, as surprised as the apprentice by the success of the attack. Feeling a mixture of anger and triumph, Marek went on the offensive to capitalize on his gain. His master's defenses quickly weakened, allowing the apprentice to cut a deep wound across Darth Vader's shoulder and another into his thigh. Despite his refusal to accept defeat, Vader was no longer capable of sustaining the fight. The apprentice telekinetically ripped the Sith's lightsaber from his hand and used the Force to lift him into the air. A barrage of missiles under the apprentice's control attacked Vader from every corner of the room, each hit stronger than the last. Then the apprentice hurled an energy field generator at his master, causing an explosion that the Sith Lord barely survived.

Moments after the blast, the apprentice emerged unscathed to find that the fight was over. Darth Vader lay gravely injured, his armor and vital respiratory system heavily damaged. Much of his mask and helmet had also been torn away by the blast, allowing the apprentice to see his mentor's true face for the first time. Marek was taken aback by what he saw as a shockingly pitiful sight: Darth Vader was actually a deformed old man whose pale skin was covered in wrinkles and old scar tissue; an amalgamation of man and machine hidden behind the armored suit. In Vader's eyes, Marek saw only agony and exhaustion.
With Darth Vader defeated and at the mercy of his apprentice, the Emperor emerged and reached out through the Force to Galen Marek. Acknowledging that Marek was a far more powerful asset than Vader, broken and diminished in the Force due to his condition, Darth Sidious encouraged the apprentice to take his revenge by striking down his former master in anger. As the Emperor's hypnotic suggestion flowed through the apprentice, Marek began to seriously consider Sidious's offer. Despite the temptation of the dark side's allure, there was a part of the apprentice that yearned to seize the title and position of a true Sith Lord.
Before he could make a decision, however, Rahm Kota charged at the Emperor in an attempt to prevent the apprentice's return to the dark side. Using the Force to steal the Emperor's lightsaber, Kota killed several Imperial Guards before attempting to kill Darth Sidious with the Dark Lord's own weapon. In response, Sidious unleashed a barrage of Sith lightning on Kota. The General's interference broke the Emperor's hold over Marek, who ultimately realized that he no longer wanted anything to do with the dark side, especially after seeing its effects on Darth Vader. Having chosen to remain with the Jedi and the Rebel Alliance, Galen Marek moved to attack the Emperor, but only to defend his friends.

The apprentice broke off the Emperor's attack on Kota by hurling pieces of broken transparisteel and debris at him. As Marek approached, Sidious praised the apprentice and urged him to embrace the dark side once more—this time by killing him. With Kota's help, the apprentice restrained himself from striking the Emperor down in anger. Before they could escape to safety, Darth Sidious attacked Kota with Force lightning once more in a final attempt to prevent Marek from joining the Jedi and Rebel Alliance.
Before Sidious could kill Kota, Marek moved in front of the lightning to protect his Jedi mentor, causing him to absorb the energy and redirect it back to its source. For a moment, both the Emperor and the apprentice were locked in an exchange of Force lightning, experiencing excruciating pain. As the Rebels retreated into the Rogue Shadow, a squadron of stormtroopers converged on the scene and tried to prevent the prisoners' escape. Their efforts were thwarted by Marek, who released a massive shock wave of energy from his own body. By the time the Rogue Shadow escaped to safety with the Rebels on board, the explosion had engulfed most of the observation deck. Although every stormtrooper within proximity of the blast was killed, Sidious and Vader both survived the explosion and began searching the wreckage until they found Marek's dead body.
Neither of the two Sith Lords were pleased by Galen Marek's demise. In addition to the Emperor's failure to replace Darth Vader with Marek, Sidious believed that the apprentice's sacrifice would inspire the Rebel Alliance to wage a full-scale galactic civil war against the Empire. Crushing the Jedi lightsaber of his fallen apprentice beneath his heel, Vader vowed to exterminate his master's enemies before the fledgling rebellion could overthrow the Sith regime.

Following the demise of Galen Marek, the Rebel leaders gathered once more on Kashyyyk, the Wookiee home planet and the very place where Darth Vader's fallen apprentice was born. Within the former dwelling of the Marek lineage, the senators—Bail and Leia Organa, Garm Bel Iblis, and Mon Mothma—decided to pool their resources to bring about the creation of the Rebel Alliance. Rahm Kota, having confirmed to Juno Eclipse that the apprentice had become one with the Force, escorted the former Imperial Captain to observe the official symbol selected by the Alliance's founders for their fresh organization; the Marek family symbol, put forward by Leia Organa as a tribute to the apprentice and his self-sacrifice for the Rebellion.
After Marek's passing, Darth Vader hatched a scheme to engineer a new iteration of his deceased apprentice—one possessing greater power and obedience than the original Starkiller. By making use of the genetic data from Marek's preserved remains, the Sith Lord endeavored to produce a duplicate capable of assuming Marek's role as Vader's personal killer. The various flaws present in the accelerated cloning process, coupled with the inherent challenges of replicating a Force-attuned blueprint, caused the project to be delayed for several months, compelling Vader to repeat the procedure multiple times until the imperfections could be rectified. This resulted in a sequence of unsuccessful clones, characterized by physical deformities and mental instability. The more stable versions underwent personal training under Vader's supervision, but ultimately failed to overcome the memory traces they inherited from their progenitor. One such clone fled Kamino in 1 BBY after his creator deemed him yet another failure. Despite the loss of the runaway clone, the project eventually yielded a single successful test subject who triumphed in his trials to become Darth Vader's new apprentice; however, the Dark Apprentice, like Starkiller, Juno Eclipse, and Rahm Kota, was never heard from again.
The confrontation itself inflicted substantial damage upon the Death Star, thereby postponing the battle station's deployment. In 0 BBY, shortly before the Death Star was obliterated during the Battle of Yavin, Vader reflected that nobody would thwart the Galactic Empire from operating the Death Star this time, recalling when Marek had damaged the station two years prior.
This battle serves as the concluding level in the Star Wars: The Force Unleashed video game. One included gameplay mechanic was the option to shove/hurl adversaries into the superlaser tube, leading to their demise via the passing superlaser, a feature desired by Haden Blackman since the level's initial designs; he likened it to pushing enemies into a subway to be killed by an oncoming train. Consequently, the tube was among the first environments finalized for the level, and the inner mechanisms of superlaser creation were then developed.
The events of the battle vary across the two game versions and the novel. In contrast to the Star Wars: The Force Unleashed novelization, where Galen Marek lands in an equatorial trench and sparks a Wookiee slave revolt, the Xbox 360/PS3 version of the game portrays the start of Marek's mission within one of the Death Star's hangars. In the PS2/Wii version, Marek lands on a bridge prior to entering the battlestation. This article endeavors to incorporate aspects from all three interpretations of the Battle on Death Star I.
Additional differences are observed in Marek's duel with Emperor Palpatine. While the Emperor wields his lightsaber against Marek in the PS2/Wii version, he solely employs Force lightning, telekinesis, and the assistance of Imperial Senate Guards and Royal Guards in the Xbox 360/PS3 version. Marek's finishing move on Palpatine also exhibited slight variations. Unlike both game versions, the novelization lacks a prolonged confrontation between Marek and Palpatine. The apprentice merely ambushes the Emperor with a telekinetic assault, prompting Palpatine to feign weakness and defeat shortly thereafter.

In the alternate, non-canon within the Legends timeline, conclusion of this battle in The Force Unleashed, Marek opts to eliminate Vader, reverting to the dark side to avenge Vader's two acts of betrayal against him and his father.
Following another extended battle, Marek disarms Vader of his lightsaber, as he did during his childhood, and pierces him with it. Marek then returns to the main platform, where the Emperor is positioned over an injured Kota. He instructs the apprentice to slay Kota to sever his ties to the Jedi, promising Marek that he would finally become a Sith Lord. Marek activates his lightsaber, prepared to strike down the blind General Kota, but, instead, in a moment of remorse, he attempts to kill Palpatine. However, Palpatine immediately ignites his own saber, effortlessly deflecting the attack, and declares that he had foreseen the attack and knew that Marek would attempt to kill him. Palpatine breaks their saber lock, lifts Marek into the air, electrocuting him for a few moments before throwing him through a window out onto the landing platform, just as the Rogue Shadow flies in to rescue the rebel leaders. Staggering on the ground, Marek sees that Bail Organa and the other Rebel leaders have already been killed. Palpatine seizes the opportunity to seize the Shadow in his grip and hurl it at Marek. It is probable that Juno Eclipse and the wounded Rahm Kota perished in the explosion.
Marek awakens on an operating table—resembling the one upon which his former master Darth Vader rested while his armor was constructed—to discover himself clad in his own suit of armor, presumably the sole element sustaining his life. The Emperor stands before him, expressing his disappointment in Marek, stating that he believed Marek could have one day become one of the greatest Sith in the galaxy, even his successor, but, now, Marek will simply be his new servant, doing the Emperor's bidding, until he is eventually cast aside, just as Vader was. Marek screams in agony as his suit is completed. Subsequently, he became Lord Starkiller, Darth Vader's successor and Emperor Palpatine's Sith Assassin. Lord Starkiller's story is then recounted in Star Wars: The Force Unleashed: Ultimate Sith Edition.