The Lost Brigade had a humble begining, starting out as Clone Trooper Brigade 43027. During the battle of Illitau, a Carbonite Freeze turret froze them, while the remains of their gunship hid them. Near the end of the Clone Wars, Jedi brothers Shwann-wan Twinn and Ryne Twinn were accompanied by a large group of clone troopers, searching for the Brigade. Order 66 came through, and, in saving Ryne, Shwann-wan wan was killed. Overcome with anger, Ryne gave in to the dark side and obliterated the clones with a massive lightning wave. By the end of the day, Ryne had an army of clones completely loyal to him. The Lost Brigade took refuge on Mandalore, adding a Mandelorian tribe to their armies. On a trip to Coruscant, Ryne recruited an orphaned child named Torag, who was a natural fighter. He also recruited a slew of Humans who showed Force potential. These he trained to be adept at the Dark side of the Force.
Throughout the years of the rise of the Galactic Empire, Ryne upgraded AT-RTs and ITFXs, along with training his men how to ride Rancor and Acklay. When he began to increase the number of planets under his control, they were brought into a galaxy of rebellion, mainly fighting the Zann Consortium, Black Sun, and Alliance to Restore the Republic. However, after the Battle of Hoth, the Brigade began to fall apart. Ryne disappeared and Torag lacked the motivation that had made Ryne great. A massive Imperial Remnant invasion force finally crushed the Lost Brigade.
Years later, a rouge Jedi known as Durzamn discovered the battered armor of a Lost Brigadier. Wearing the armor, he named himself Durzamn the Resurrector, starting a group of elite warriors known as the Found Brigade. This group, too, was crushed by the Empire. But it was ever as great as the Lost Brigade.