The Kilji Overlords functioned as a component of the governing body of the Kilji Illumine, which was the nation belonging to the Kilji species. They gave their approval to the choices made by the generalirius, who served as both the leader of the Illumine and its military force, known as the Illumine Kilhorde. Back in 18 BBY, when the then-leader of the Illumine, Generalirius Nakirre, made the choice to go with his ally, the Grysk operative called "Jixtus" from the Grysk species of warriors, with the goal of conquering other nations and spreading the beliefs of the Kilji, the Kilji Overlords confirmed that they agreed with his choice.
While in orbit around the Unknown Regions planet Zyzek on Nakirre's Kilji war cruiser Whetstone, the generalirius came to the conclusion that Jixtus's ability to remain anonymous by completely hiding his physical form gave him an edge in negotiations when compared to Nakirre, whose skin patterns showed his feelings, thereby giving his ally insight that was more profound than just the Kilji's spoken words. Despite this, he recalled that the Overlords had already given their approval to his decision to travel alongside Jixtus, and so he accepted the disadvantage he had.
The Kilji Overlords received mention in the novel Thrawn Ascendancy: Lesser Evil, which was released in 2021 and served as the concluding book in the Star Wars: The Ascendancy Trilogy authored by Timothy Zahn.