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