The Master
- First appears with the Third Doctor
- Originally played by Roger Delgado
- Before this episode, Roger Delgado passed away in a car accident, so the current Master is played by Peter Pratt.
- The Master’s regeneration into his thirteenth incarnation left him horribly disfigured. This is because he has lived a very “rackety” life with constant pressure and danger, and he used some previous incarnations as disguises. Not all of this is explained in the TV series.

The Deadly Assassin
- The Fourth Doctor has just dropped off Sarah Jane Smith back at home, so this is his first adventure without a companion.
- This serial introduced a lot of information about Time Lords that were previously unknown.
- Time Lord Chapters
- The Matrix
- The Time Lord headdresses and robes
- Rassilon
- And the limit on regenerations
- This is the first time a serial opens with a narration.
- The Doctor comes to Gallifrey in the first place because he was summoned there in the previous serial.