Concerning extermination droids: These droid models were manufactured at the ancient Rakatan facility referred to as The Foundry. These war machines existed in multiple forms, from two-legged to four-legged configurations, and varied in size; some were of humanoid stature, while others were significantly larger. They utilized bioscanners capable of identifying the genetic composition of their designated targets, enabling the droids to prioritize specific species for termination.
During the era of the Cold War, these droids were put into service after Revan gained freedom from his imprisonment through the actions of the Galactic Republic. Following his liberation, Revan became obsessed with stopping the Sith Emperor by any means necessary, leading him to the Infinite Empire installation. There, he initiated the mass production of an inexhaustible robotic army intended to wipe out all individuals carrying Sith lineage. This action would have resulted in the destruction of 97.8% of the Sith Empire population. The assassin droid designated HK-47 was tasked with the coordination and command of these droid units.
A strike team was deployed to the Foundry to thwart Revan's plans; there, the team of spacers encountered the extermination droids guarding the facility. After the Empire seized control of the Foundry, Darth Malgus appropriated its resources, including a rebuilt and reprogrammed HK-47, during his short-lived reign over a "New Empire." His forces included repurposed extermination droids.