The Imperial Legion is a group of foot soldiers who do the the work considered too dangerous for regular soldiers. It is comprised almost entirely of members of the lower classes of the empire. They are recruited with the promise that if they finish 5 years of service they will be rewarded with a pension and membership in the upper classes.
The mortality rate in the Legion hovers around 99%. Not only due to the incredibly dangerous nature of their missions but also the drug 2X. The drug gives the user increased strength, perception and ferocity. Prolonged use can also cause the circulatory system to shut down or the heart to explode.
You can always tell a veteren of the Legion by their eyes. Prolonged exposure to 2X causes the eyes to become discolored and malformed. The overall effect is difficult for most people to look at.