Fratalin

 worked on Amethyst Viral Containment Station. He was a multiple entity made up of eight hundred individuals. He kept on talking about the Viyrans and their work. His voice was assimilated into their vocal banks.

When the Daleks invaded the Amethyst Viral Containment Station, Fratalin's familiars engaged them in combat. They were capable of working together to consume individual Daleks, rendering them helpless. However, many of the familiars were exterminated in the conflict. This caused Fratalin to behave more erratically.

After Mila-Charley rendered the Sixth Doctor unconscious, he failed to create an explosion to stop the Daleks before the their time conduits exploded. (AUDIO: Patient Zero)