Project ZEUS was a top-secret, classified October-Gray project made in the year 2015 to test if certain augmenting drugs were given to select-few UN or NATO soldiers in the world, if the soldiers would be enhanced in any way. Codename: CASTLE was given these drugs first.
For Castle, it proved to make the once-normal 101st airborne shock trooper into a hyperlethal "supersoldier."*
However, for five of the six other ZEUS candidates, it didn't fare so well. One of the candidates was killed, and four were permanently disabled. The last one managed to survive, but would sometimes experience sudden spasms. These spasms did not affect his health, but it proved to be very ineffective during combat. During one of these spasms in 2017, he was killed. Castle managed to live until 2022, before his sudden mysterious disppearance.
- Pardon me for Halo references, but I just love Halo.