The Rise of the 501st Legion
Initially, it was the 501st Clone Battalion. Later, Vader's Fist was its nickname. Then it was renamed as 501st Imperial Legion. Dark Lord of the Sith Darth was its commander in Imperial Era. This Legion predated Galactic Empire. It fought against the Separatist Droid Army. Jedi General Anakin Skywalker, Jedi Commander Ahsoka Tano, and Clone Commander CT-7567 served as the leaders. The Legion was famous for loyalty to the Galactic Republic, courage, and tactics. They fought multiple battles across the galaxy. They include the Battle of Christophsis, the Second Battle of Geonosis, and the Battle of Umbara. General Pong Krell started to betray the Legion. His betrayal was later revealed, and in military custody, he was executed. Against the Jedi Order exposed a Sith conspiracy. General Tiplar was betrayed and killed in the Battle of Rindo Vinda CT- 5385.
The Dark Days
At the end of Clone Wars, the 501st was divided by Skywalker. 332nd Division and 332nd Company were formed. The division Commander Rex defeated the super commandos of Mandalorian. Sith apprentice Maul was captured, who was their leader. The great Jedi purge started when Order 66 was in effect. Supreme Chancellor Sheev Palpatine declared it. It causes the clone troopers to be against their Jedi officers. Half of the Legion attacked the Jedi Temple and killed its people. They include Jedi younglings and Padawans. The leader of the half Legion was Sith Lord Darth Vader. Rex tried to defend Tano against his army. 501st was almost emptied because of carrying out Order 66. Jedi Masters Yoda and Obi-Wan Kenobi defeated the Legion on Coruscant. The Legion was later dissolved into Imperial Military.