During the Desolator crisis, which occurred in 3643 BBY, Valis, a Sith, orchestrated a scheme to ensnare Kira Carsen, a Jedi Padawan, and her master. His trap led them to a deserted mining facility situated in the Outer Rim, where he forced them into a duel. Valis, an agent known as a Child of the Emperor and acting under the orders of the Sith Emperor himself, aimed to reclaim Carsen, a former Child, and bring her back under the Emperor's control. Carsen and her Jedi Knight instructor, under the impression they were meeting Admiral Hacklin of the Sith Empire to discuss his potential defection, journeyed to the space station. Instead, they encountered Valis, who met his death in the ensuing combat. The duel resulted in Carsen revealing her hidden past to both her master and the Jedi Council, providing the Jedi Order with tangible evidence of the Children's existence.
Kira Carsen's origins trace back to Dromund Kaas, a planet serving as the capital of the Sith Empire. As an infant, she was handed over to the Sith Academy on Korriban. During her childhood, the Sith Emperor selected her to be one of his Children, who unknowingly served as his eyes and ears across the galaxy. However, Carsen managed to escape the Empire before the process was complete, leaving behind other Children like Valis and Suri. She found her way to Nar Shaddaa, a moon, and lived on the streets before joining the Jedi Order, concealing her past and Imperial connections for fear of expulsion.
In 3643 BBY, Darth Angral, a Sith Lord, initiated a war against the Galactic Republic and the Jedi Order as retribution for his son Tarnis's death at the hands of Carsen and a young Jedi Knight. Angral seized control of several Republic superweapons, prompting the Jedi Knight and Carsen to pursue Angral's agents throughout the galaxy. During this time, the Knight took on Carsen as a Padawan, since Carsen's previous Master Bela Kiwiiks was occupied with her own assignment. While the Knight was on a mission on Ord Mantell, Carsen remained on the Ord Mantell Orbital Station, where an Imperial operative identified her as the Knight's apprentice and informed Darth Angral. Angral, along with his retainers, including Admiral Hacklin of the Imperial Navy, arrived and interrogated Carsen about the Knight's location. However, Carsen deceived the Sith Lord, leading him to Corellia. Although Carsen escaped Angral's servants with her teacher's help, Angral recognized her as a former Child, and the Emperor learned of her survival.
Driven to recapture Carsen, the Emperor sent Valis, another of his Children, to bring her back. Valis, impersonating Admiral Hacklin, contacted the Republic and offered to defect, but only to Carsen and her master. General Var Suthra arranged a meeting between "Hacklin" and the two Jedi at a deserted mining facility previously run by the Czerka Corporation in the Unknown Regions. Valis arrived before the Jedi, concealing himself among cargo crates in the facility's hangar after disembarking from his ship. As the Jedi approached, he observed them before revealing himself and addressing them. After introducing himself and expressing gratitude for their arrival, Valis apologized for the deception. Carsen immediately recognized him and warned her Master to attack. Amused, Valis revealed that Carsen was also a Child of the Emperor, and that their "father" wanted his wayward Child to return.
The Knight refused Valis's demand to surrender Carsen, and the Padawan attacked the Sith, bringing her double-bladed lightsaber down on his head. Valis, however, summoned his own lightsaber and blocked the attack before using telekinesis to push her back. The Knight rushed to Carsen's defense, and a battle ensued. Despite Valis's combat skills and command of telekinesis and Force lightning, he was ultimately defeated by the combined strength of Carsen and the Jedi Knight, resulting in his death.
After returning to their ship, Carsen confessed her past to her teacher, and together they revealed it to the Jedi High Council. Despite Master Jaric Kaedan's desire to expel her from the Jedi Order, Grand Master Satele Shan permitted Carsen to continue as the Knight's apprentice, although General Suthra remained cautious about her involvement in future operations. During the climactic confrontation with Angral in a battle over Tython, Angral was killed by the Knight. However, the Emperor reached out to Carsen, his former Child, and completely possessed her. With her teacher's assistance, Carsen managed to expel the Emperor and sever their connection.
The duel with Valis was first featured in the Jedi Knight class mission "The Defector" in Star Wars: The Old Republic, a video game that was released in 2011. This mission serves as the intermission of the Act I story, connecting the class storylines on Nar Shaddaa and Tatooine.