Doctor Who: The Newbies Guide
State of Decay
This is the fourth 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.
Romanadvoratrelundar (or Romana for short) is a Time Lady. In The Ribos Operation, the White Guardian transported her onto the Doctor's TARDIS to help him in his quest for the Key to Time. In Destiny of the Daleks she regenerated into a new form. This version of Romana is fun-loving and definitely on a par with the Doctor.
K9 Mark 2 is a robotic dog built by the Doctor. In The Invasion of Time, the Doctor left the original K9 on Gallifrey. K9 is very literal in his thinking and is programmed to obey his master and mistress.
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
This story features actual vampires, which conform to many of the modern versions of vampire myths and stories. They have not previously appeared in Doctor Who.