Doctor Who: The Newbies Guide
The Stones of Blood
This is the third story in Season 16.
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.
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, though she believes that the High President of the Time Lords gave her this task. She has more book smarts but less practical experience than 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.
Recurring and Historical Characters
The White Guardian is the cosmic entity who sent the Doctor and Romana on their quest for the Key to Time.
In The Ribos Operation a cosmic entity known as the White Guardian gave the Doctor the mission of collecting the pieces to the Key to TIme in order to restore the cosmic balance. The pieces are disguised as different things scattered throughout space and time.