Doctor Who: The Newbies Guide
The Keeper of Traken
This is the sixth story in Season 18.
The Fourth Doctor dresses in a rather bohemian outfit, notable for its long scarf. He is somewhat alien, willing to play the fool, and almost never gets on with authority figures. In The Armageddon Factor, the Doctor fitted a Randomiser to the TARDIS in order to stop a cosmic entity called the Black Guardian from finding him.
Adric is from the planet Alzarius in E-Space. He is a mathematical genius from a race with a high metabolism (which means he heals fast). In Full Circle he stowed away on the TARDIS.
Recurring and Historical Characters
The Master is a Time Lord and an enemy and rival of the Doctor. In Terror of the Autons he arrived on Earth and allied with the Nestene Consciousness to attempt to conquer Earth. He was stopped by the Doctor and UNIT. He has since come into conflict with the Doctor on many occasions. In The Deadly Assassin we saw that he had been reduced to a deathly husk as a result of a failed regeneration.