The 501st Legion was a legion of clone troopers and later stormtroopers in the Galactic Empire. They were an elite legion, and saw action alongside of Darth Vader. They were also called Vader's Fist. The 501st saw many missions, but in the game, they are only seen on Kashyyyk when Galen Marek was found by Vader while searching for a rogue Jedi.