Doctor Who: The Newbies Guide
Planet of Fire
This is the fifth story in Season 21.
The Fifth Doctor is physically younger than his previous incarnations. He wears Edwardian cricketing clothes with a stick of celery on the lapel. He is less eccentric than his previous incarnations. In Earthshock he was unable to save his companion Adric from dying.
Vislor Turlough is an alien who was exiled to Earth. He was posing as a schoolboy at Brendon School. In Mawdryn Undead he made a deal with the Black Guardian to kill the Doctor in exchange for returning home. He did not manage to do so during that story but did stow away on the TARDIS and then ask the Doctor to allow him to join him on his travels. In Enlightenment he cancelled the deal. We have never learned anything substantial about his background before arriving on Earth.
Kamelion is a shape-shifting android. In The King's Demons, the Master used him in a plot to prevent the signing of the Magna Carta. The Doctor took him aboard the TARDIS. Since then he has not been seen onscreen (there was one story where he appeared in some deleted scenes).
Perpugilliam "Peri" Brown is a new character. This is her first appearance.
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 Keeper of Traken he was reduced to a deathly husk, and then possessed the body of Tremas of Traken. In Logopolis he unleashed a wave of entropy that destroyed a large portion of the universe, including Traken. His actions were also responsible for the Doctor's most recent regeneration.