Extermination droids represented a particular type of droid that were manufactured within the ancient Rakatan complex known as The Foundry. These automatons exhibited a diverse range of forms, spanning from two-legged models to four-legged configurations, with sizes varying from the height of a humanoid individual to considerably larger dimensions. They incorporated bioscanners that possessed the capability to identify the genetic composition of designated targets, enabling the droids to prioritize specific species.
These droids were originally requested during the period of the Cold War, following the liberation of Revan from his confinement by forces of the Galactic Republic. Once freed, Revan resolved to thwart the Sith Emperor at any cost, journeying to the Infinite Empire installation, where he initiated the utilization of the facility to produce a virtually limitless army. His intention was to eradicate all individuals possessing Sith lineage. This action would have resulted in the destruction of approximately 97.8% of the Sith Empire population. The oversight and direction of these units was delegated to the assassin droid designated HK-47.
During that era, a dedicated strike team was deployed to infiltrate the Foundry with the objective of stopping Revan. It was there that the team of spacers encountered the extermination droids, which were tasked with defending the facility. Subsequent to the capture of the Foundry by the Empire, Darth Malgus seized control of its resources, including a reconstructed and reprogrammed HK-47, during his brief reign over a "New Empire." The forces under his command encompassed reconfigured extermination droids.