Klegger Corp Droid Army
From Wookieepedia, the Star Wars wiki.
The Klegger Corp Droid Army was a droid army that Gizor Dellso found on Mustafar. He reactivated it and used it to combat the Galactic Empire. The army consisted of B1s, B2s, Droidekas and MagnaGuards. In response, Darth Vader sent the 501st to assassinate him and shut down his whole operation. In the Battle of Mustafar, the droids were deactivated and the factory was destroyed, making sure no more could be manufactured.
