Characters

Brain: The Brain, used by the Rani to calculate the right launch time and trajectory for her missile
Channing: Channing, a figurehead for the first Auton Invasion
Lytton: Lytton, a mercenary for hire who worked for the Daleks and against the Cybermen
Sil: Sil, one of the evil Mentors
The Master: The Master, another renegade Time Lord
The Rani: The Rani, a renegade Time Lady from Gallifrey
The Valeyard: The Valeyard, the dark side of the Doctor, somewhere between the twelth and thirteenth regenerations