These aberrant clones represented genetically imperfect versions of Galen Marek, a Human male Force-sensitive individual. Marek had been the secret apprentice of Darth Vader, a Sith Lord, until his redemption and subsequent death in 2 BBY. Vader's ambition was to overthrow his own Sith Master, Emperor Palpatine. To that end, he attempted to fashion a new apprentice. He planned to use Marek's deceased form as a template to create a clone who would inherit all of Marek's combat prowess, but without any emotional ties, and with unwavering loyalty to the dark side of the Force.
Vader's scientists employed an experimental iteration of the Kaminoan cloning methodology to replicate Marek's genetic code. However, they encountered substantial difficulties due to the attempt to clone a Force-sensitive subject. The initial subjects displayed physical deformities and were driven insane due to the inherent memories they received from their genetic source. The Lead Cloning Technician gradually refined the procedure, eventually producing a new group of clones that bore a physical resemblance to Marek at the time of his demise. Despite this improvement, these clones still experienced an identity crisis stemming from the memory flashes intended to facilitate their training. Ultimately, these flawed clones were maintained in stasis within the cloning facilities located in Timira City on the planet Kamino. Vader personally supervised the training of clones that exhibited potential, discarding those he deemed failures in his pursuit of a clone who met his rigorous standards.
In 1 BBY, the Alliance to Restore the Republic launched an attack against the Timira City cloning facility. They were aided by "Starkiller," a rebellious clone who had fled from Kamino after Vader rejected him as another failed experiment. During his mission to rescue Juno Eclipse from Vader, this rogue clone encountered several aberrant clones. While Starkiller prevailed against the clones who attacked him, he viewed their deaths as a form of fratricide, considering their shared genetic origin. He also recognized the mental instability plaguing his clone brethren, having personally grappled with his own identity crisis due to the memories of another man's life.
The genesis of the aberrant clones can be traced to a clandestine endeavor aimed at replicating the deceased Galen Marek, formerly a Sith apprentice serving under the Sith Lord Darth Vader. Shortly after Marek sacrificed his life to protect the founders of the Rebel Alliance—including senators Mon Mothma, Garm Bel Iblis, Bail Prestor Organa, and Jedi Master Rahm Kota—Vader transported Marek's remains to the planet of Kamino. His intention was to preserve the body as a template from which to extract the necessary DNA for cloning.
The project's success was hampered by numerous challenges. First, the Dark Lord's scientists opted for an accelerated cloning process, an experimental technique that produced fully developed subjects in a matter of weeks. The disadvantage of this method was that all clones created through it were prone to succumbing to madness due to their rapid growth cycle. Another problem that perplexed the cloning technicians was the nature of the Force itself. By that point, it was widely believed that cloning Force-sensitive individuals was inherently problematic. While the exact reason for this was unclear, Ni-Ke-Vanz posited that the Force itself interfered with the cloning process. The third, and most significant, obstacle was memory. For the new apprentice to effectively utilize his inherent Force powers and combat skills, Marek's memories would need to be imprinted onto the clone's mind, transferring his knowledge and experience. However, this process also risked creating an identity crisis in the clone, as he would possess the memories and emotions of another individual.
Despite these challenges, Darth Vader pressed forward with his plans. The initial results yielded hundreds of aberrant clones, all physically deformed and mentally unstable, and none of whom met Vader's or his lead cloning technician's standards. These flawed clones were placed in suspended animation within their cloning tanks, allowing for gradual correction of their design flaws to produce less imperfect clones. Simultaneously, Vader personally trained several promising test subjects, hoping that at least one clone would prove suitable to become his new apprentice.
After months of unsuccessful attempts, the project was finally considered a success when a single clone triumphed where all his predecessors had failed: he overcame the imprinted memories of Galen Marek. By compartmentalizing and isolating Marek's memories, he managed to distinguish his progenitor's thoughts from his own. Around the same time, another clone had come close to succeeding in his own trials, only to disappoint Vader due to his persistent attachment to Captain Juno Eclipse, a trait that his successful counterpart also shared but later suppressed. Realizing that he would be discarded as a failed experiment, the rebellious clone managed to escape from Kamino, only to return later leading the Rebel Fleet to rescue Captain Eclipse.
As the battle commenced, Boba Fett, a cloned bounty hunter employed by Darth Vader, encountered a lone aberrant clone wielding a red-bladed lightsaber. Fueled by mindless rage, the clone attacked and nearly killed Fett, only to be defeated when Fett desperately launched a missile from his Z-6 jetpack at the clone.
During the conflict, the rebellious clone—now known as "Starkiller," the original codename of his template—infiltrated Timira City, where he was confronted by Darth Vader and the aberrant clones. Until that moment, Starkiller had not believed that other clones existed before him. The sight of his "brothers," however flawed, forced him to confront a truth he had always suspected: he was a clone, and the original Starkiller was dead, as Vader had told him. The only emotions he sensed from the aberrant clones were hate, rage, and an overwhelming desire to kill. Yet, they also displayed confusion, all equally uncertain about their own identities.
While defending himself against the clones, Starkiller observed his predecessors. He noticed that the first wave of attackers were the weakest and easiest to defeat. The second group was more cautious, maintaining their distance from their target, who was armed with dual lightsabers. The final waves included clones who wielded Force lightning, and others trained in lightsaber combat. Despite possessing Marek's Force sensitivity, none could overcome the rebellious clone in open combat. Those who charged at him were cut down, others were overwhelmed by his own command of the Force, and the rest turned on each other due to their unstable minds.
As the Assault on Kamino concluded with a decisive Rebel victory, Starkiller successfully rescued Juno Eclipse and defeated Darth Vader, who was subsequently taken into Alliance custody. Despite his success, Starkiller remained troubled by his encounter with the aberrant clones. Aside from their differences with him and each other, they all shared Galen Marek's attributes to varying degrees. Consequently, Starkiller struggled with guilt over killing the aberrant clones, an act he considered a form of fratricide—even suicide, given that they were all genetic copies of the same man.
Despite their genetic imperfections, the aberrant clones possessed Galen Marek's potent connection to the Force. However, the psychological damage they sustained during the cloning process prevented them from effectively channeling Marek's abilities in a focused and controlled manner during combat. As the earliest and most flawed clone iterations, the genetically inherited abilities of the original Starkiller were not uniformly distributed among the aberrant clones.
Some clones excelled at utilizing Force attacks such as Force lightning and Force push. Others were equipped with dual lightsabers and specialized in the Jar'Kai fighting style. All of the aberrant clones, however, could shield themselves from basic Force attacks, with the exception of Mind Control. Nevertheless, they were vulnerable to the full force of a Force Repulse when employed by the rebellious clone, as evidenced by their disintegration into a fine bloody mist.
In the Xbox/PC/PS3 versions of the game, the aberrant clones' lightsabers are fitted with silver crystals. In the Wii version, their lightsabers are colored purple, red, or orange. These color variations help players discern which clone employs which technique. Clones with red lightsabers specialize in melee combat, those with purple lightsabers use Force Lightning, and those with orange lightsabers use Force Push, as demonstrated by how they break free from their tanks to attack Starkiller upon hearing the sound of Force Repulse.