A member of the Kilji species, designated "Vassal One," was a loyal Kilji vassal serving the Kilji Illumine nation. As such, he adhered to the religious beliefs of the Illumine. During 18 BBY, he functioned as a pilot on the Kilji war cruiser Whetstone, under the command of Illumine Generalirius Nakirre. While the war cruiser was in orbit around the Unknown Regions planet Zyzek, Vassal One adjusted the vessel's orientation to face the Chiss heavy cruiser Springhawk. Subsequently, he navigated the Whetstone to a star system within the Unknown Regions and the Unknown Regions planet Ornfra.
A Kilji called "Vassal One" was in service to the Kilji Illumine nation as a Kilji vassal, a follower of their religion, specifically the Kilji way of order and enlightenment. He was the pilot of the Kilji war cruiser Whetstone, which was under the command of Generalirius Nakirre, the Illumine's leader. In 18 BBY, the Whetstone journeyed to the Zyzek system in the Unknown Regions. As the warship was orbiting the planet Zyzek, the Chiss heavy cruiser Springhawk made its appearance. Following advice from "Jixtus," a Grysk operative and Nakirre's ally, who cautioned against speaking with the Chiss commander, Senior Captain Mitth'raw'nuruodo (whose core name was "Thrawn"), Nakirre instructed Vassal One to rotate the Whetstone to face the arriving ship. The vassal obeyed, and the generalirius spoke with Thrawn. After the Kilji leader's conversation with the Chiss officer, his cruiser departed Zyzek.
Jixtus, promising to provide answers to Nakirre's inquiries, requested that the generalirius bring his vessel to a specific star system located within the Unknown Regions. Nakirre directed Vassal One to comply with the Grysk's request, and the vassal followed through. The vassal communicated that the voyage would take thirty-five minutes; however, Nakirre ordered his vassal to bring the Whetstone to the system in ten minutes. Upon their arrival at the designated system, Vassal One issued a warning, and Jixtus's FateSpinner flagship materialized in front of the Kilji ship. The Grysk operative threatened the Kiljis with destruction if Nakirre refused to follow his orders, thereby compelling the generalirius to agree to the Grysk's demands. After the Whetstone made a visit to Rhigar, a planet belonging to the Chiss Ascendancy, Jixtus gave Vassal One instructions to guide the Whetstone to the Chiss world of Ornfra.
Since Nakirre's vassals were bound to his commands, the Kilji remained silent until the Kilji leader verified the Grysk's instruction, which Vassal One then executed. Soon after, the Whetstone met with Jixtus's fleet in the outer "Sunrise" system, a region within the Unknown Regions. Jixtus instructed his personal navigator, Pathfinder Qilori, to execute an in-system jump to transport the Whetstone to the planet "Sunrise." Nakirre suggested to his ally that Vassal One was capable of navigating them to Sunrise; however, the Grysk insisted on Qilori's involvement, and the Pathfinder ultimately guided them to the planet.
Vassal One, being a Kilji vassal, adhered to every order given by Nakirre. When Nakirre instructed him to navigate the Whetstone to a star system in the Unknown Regions within a span of ten minutes, the vassal displayed visible concern and surprise; nevertheless, he proceeded to fulfill his generalirius's directive.
Vassal One made an appearance in the 2021 novel Thrawn Ascendancy: Lesser Evil, which is the concluding book in the Star Wars: The Ascendancy Trilogy penned by Timothy Zahn.