Hosk Trey'lis, a male Bothan Jedi Knight and healer, was one of the Jedi who worked on the Ossus Project—the project to have the Yuuzhan Vong terraform the worlds that had been ravaged by their invasion of the galaxy. After the project was sabotaged in 127 ABY by the One Sith, who had allied themselves with the Fel Empire, a war broke out between the Empire and the Alliance. Trey'lis managed to avoid the massacre of the Jedi Order on Ossus at the end of the Sith-Imperial War, and spent the next seven years on the run. In 137 ABY, Trey'lis was waiting in Brogar's cantina on the planet Lok for transport offworld when bounty hunter and former Jedi Cade Skywalker, along with fellow hunters Jariah Syn and Deliah Blue, burst into the cantina, seeking to capture the gambler Naxy Screeger. Trey'lis believed the bounty hunters were after him, and attempted to flee. Recognizing the Bothan was a Jedi, the hunters captured Trey'lis, and he was turned over to the Sith for the bounty cast upon living Jedi.
In the Temple of the Sith on the galactic capital of Coruscant, Trey'lis was tortured and interrogated by Darth Maladi, the head of Sith Intelligence and Assassination. Unable to resist her ruthless interrogation and torture techniques, Trey'lis eventually told her everything he knew about young Skywalker, whom Emperor Darth Krayt, the reigning Dark Lord of the Sith, sought for his healing ability. After having a vision of the Bothan, Skywalker traveled to Coruscant to rescue Trey'lis, only to get captured himself. A week later, after pretending to join Krayt and receiving training as a Sith, Skywalker attempted another rescue, but was once again thwarted. Both Trey'lis and Skywalker were taken to Krayt's chambers, where the Dark Lord attempted to convince Skywalker to kill the Bothan as a show of devotion to the Sith. Not wanting to be used as a weapon, Trey'lis pleaded with Skywalker not to turn to the dark side. Krayt then struck the Bothan down, and Trey'lis's body disappeared as he became one with the Force.