At first, X-4 became friends with X-1, X-2, X-3, X-5, X-6, and X-7, the other participants in the training program. However, after Soresh started torturing them with electrocution, X-4, like the others, had his personality and mind changed completely until he felt no emotions. Around 10 BBY, they were pitted against each other in combat until only one remained. X-4 committed suicide by hanging himself with a laser whip. X-7 later earned the right to become Soresh's personal assassin.
X-4 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-4 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.