The 501st Legion functioned as a stormtrooper unit belonging to the Empire of the Hand military. The initial 501st Legion, an exceptional force largely made up of clone soldiers derived from the Jango Fett template, played an indirect role in the establishment of the later unit bearing the same name. Upon the instruction of Senior Captain Thrawn, the Hand of Judgment—a collection of rogue stormtroopers including Daric LaRone, Korlo Brightwater, Taxtro Grave, Saberan Marcross, and Joak Quiller—were responsible for training a new 501st Legion that accepted both naturally birth-born Humans and various aliens.
While the original 501st was disbanded after the collapse of the First Galactic Empire, its successor endured, guaranteeing that the 501st persisted as an elite Imperial soldiers unit.
The formal reestablishment of the 501st was executed by Senior Captain Voss Parck, fulfilling Thrawn's desire to see the legion restored within the Empire of the Hand. Among the legion's components was Unit Aurek-Seven, a stormtrooper squad involved in the Empire of the Hand's liberation of Kariek.
Daric LaRone, an Imperial stormtrooper, killed his ISB Major, which caused him and other stormtroopers to flee from the Galactic Empire. This group of deserters became known as the Hand of Judgment. Senior Captain Thrawn took notice of their skills and their acceptance of aliens, so he offered them the task of training the next generation of stormtroopers for the Empire of the Hand.