Castel's background is unknown but he, along with, many others, have been part of the Treadstone project and had extreme military and strength training to roughly kill his targets. Castel is also a trusted operative for the CIA as he was contacted by them to eliminate their big threat, Jason Bourne.
HistoryMarie Helena Kreutz to his old apartment and blasts through a window, using a submachine gun and a knife, to engage Bourne in hand-to-hand combat. Bourne uses a ballpoint pen to deflect strikes from Castel's knife. Bourne stabs Castel in the hand with the pen and it penetrates the skin on the back of his hand, entering his wrist. This does not deter Castel and he pulls the pen out and returns to the fight. Unfortunately, weakened by the repeated blows, as well as possible blood loss, Bourne rapidly subdues him, breaking Castel's arm and leg. He then attempts to interrogate him, but Castel jumps out the window, preferring suicide. Marie finds wanted posters in Castel's bag with both her and Bourne's pictures on them. After leaving the apartment, Marie and Jason go into hiding.
Castel appears as a boss fight in the video game The Bourne Conspiracy. The boss battle resembles the fight between Bourne and Castel in the film The Bourne Identity. As in the film, Castel uses his knife and martial arts skills to battle against the Bourne. The boss battle ends in a similar fashion as the film as Castel commits suicide by jumping out the window but the player must defeat Castel by depleting all of his stamina.
- Although, Castel wears a shoulder holster for two handguns, he doesn't seem to use them in the apartment fight.