Yuun, a male Gand who breathed with the assistance of a device (breathing), served the Galactic Republic as a technical engineer. This occurred during the period of the Cold War with the reconstituted Sith Empire. In accordance with the customs of his species, he referred to himself as simply Gand when experiencing shame. He was recruited into Havoc Squad on Hoth at the onset of the Galactic War. Sergeant Yuun remained a member of the unit until his commanding officer vanished in 3636 BBY. After this disappearance, Yuun spent a year fruitlessly searching the Unknown Regions for his commander, after which he departed from the Republic Military and commenced studying the technology of the Eternal Empire.
Yuun, a Force-sensitive Gand originating from his species' homeworld, underwent training as a Findsman within the shamanistic order. Possessing exceptional technical skills, Yuun made what he deemed a logical decision: he left his homeworld to enlist in the Republic Army during the Cold War that followed the Great Galactic War. While training with the forces of the Galactic Republic, Yuun utilized his Findsman abilities to discern omens, which facilitated his rise through the ranks and allowed him to achieve a series of significant accomplishments. Despite the effectiveness of Yuun's methods, they were seldom understood or approved of by his fellow soldiers. Nevertheless, his fighting prowess and composed demeanor in the face of adversity generally garnered him at least the reluctant respect of those with whom he served.
Positioned on Hoth as a member of Havoc Squad due to an assignment by General Elin Garza, Yuun received the task of neutralizing the Imperial superweapon known as the Gauntlet. By reassembling an Imperial device known as the umbra encrypter to decipher Imperial codes, Yuun successfully demonstrated his value to his comrades, leading to his acceptance into the squad.
Subsequent to the disappearance of Havoc Squad's commanding officer during the Eternal Empire's invasion, Havoc conducted a year-long search for their leader before ultimately disbanding. Tanno Vik reverted to a life of crime, Forex was summoned to serve in the Press Corps, and Elara Dorne was removed from Havoc by Chancellor Saresh. Ultimately, Yuun departed from the military and journeyed to Zakuul with the intention of gaining a comprehensive understanding of Zakuulan technology. By 3631 BBY, the Outlander approached Yuun, acting upon the recommendation of Juvard Illip Oggurobb, with the aim of recruiting him into the Alliance that opposed the Eternal Empire. Yuun was in the process of reconstructing a device designed to cloak the Alliance base situated on Odessen from the long-range sensors of the Eternal Empire. Having already acquired the initial seventeen components, he sought the Outlander's assistance in locating the remaining three. The Outlander successfully completed this task, and subsequently, the two departed Zakuul for Odessen. Upon their arrival, Yuun utilized his intuition to assist Oggurobb in locating a precision torque-spanner that he had misplaced several months prior, before identifying a solution to a thruster heat dissipation issue that the Hutt scientist had been unable to resolve for a month.
Within the Imperial narrative, Yuun departs from the Alliance following the events of Jedi Under Siege due to the Alliance's perceived recent alignment with the reconstituted Sith Empire. He requested that this not be a source of sorrow for the Commander. Nevertheless, he left open the possibility of future collaboration with the Commander should their paths happen to cross once more.