At first, X-5 became friends with X-1, X-2, X-3, X-4, X-6, and X-7, the other participants in the training program. However, after Soresh started torturing them with electrocution, X-5, like the others, had his personality and mind changed until he felt no emotions. Around 10 BBY, the trainees were pitted against each other until only one remained. X-5 malfunctioned and began muttering about alliances. He encouraged the others to see Soresh as their enemy. Just before all of X-7's emotions had gone, he killed X-5, earning the right to become Soresh's assassin.
X-5 appeared in a flashback sequence in Rebel Force: Target, the first book of the young readers series Star Wars: Rebel Force, published in 2008 and written by Alex Wheeler.
X-5 appeared in a flashback sequence in Rebel Force: Target, the first book of the young readers series Star Wars: Rebel Force, published in 2008 and written by Alex Wheeler.