Dr. Mulus Cheems, a mineral analyst of the male persuasion, was held as a prisoner on Ryvester in 13 ABY by none other than Imperial Admiral Kosh Teradoc. Teradoc's purpose for holding Cheems was to task him with investigating methods for remotely deactivating the crystals within Jedi lightsabers utilizing a sonic device. Although Cheems discovered that the lightsaber hilts possessed too much insulation for this to be feasible, he chose to withhold this information from Teradoc, understanding that his usefulness to the admiral, and therefore his life, depended on it. Wraith Squadron eventually rescued him from Teradoc's control at a Ryvester bar, after they had tricked the admiral with a fake artifact of little worth. Cheems falsely claimed the artifact was real, knowing full well it was not. At the bar, Teradoc betrayed Wraith Leader Garik Loran, who was undercover as a smuggler offering the artifact in exchange for Teradoc's help in retrieving more from the Palace of Piethet Brighteyes hoard. Loran responded by summoning the rest of Wraith Squadron and detonating a small explosive containing an eye irritant. The Wraiths subdued Teradoc's forces, created an escape route, and took Cheems with them to one of Teradoc's yachts, which they then commandeered.
Following Cheems' liberation, the members of Wraith Squadron revealed that their mission encompassed not only his rescue but also the assassination of Teradoc using the false artifact. The artifact was actually a series of interconnected explosives, designed to detonate once secured within the admiral's base. The explosives proved effective, leading to the destruction of Teradoc and a vault filled with bioweapons.
Years later, in 44 ABY, Cheems assisted the reformed Wraiths by supplying gems for a disguise created for Clawdite actor Turman Durra. The Wraiths were devising a scheme to lure the treacherous General Stavin Thaal to Kuratooine. Cheems' adopted Yuuzhan Vong son, Viull Gorsat, who was then a member of Wraith Squadron, engineered Durra's disguise. This allowed the actor to impersonate a local sentient species that had recently awakened from a prolonged hibernation and was supposedly interested in a profitable trade involving valuable gem-encrusted 'art' with the general. Thaal was drawn to Kuratooine by Durra's ruse and the promise of gems, enabling the Wraiths to dismantle his extensive illegal operations. The deception proved successful, ultimately leading to Thaal's exposure, disgrace, and capture.
Aaron Allston conceived Cheems for X-Wing: Mercy Kill, the tenth book in the X-wing novel series.