Question: What science fiction character featured in "Doctor Who" is featured in an original novel written by Christopher Bulis?

Context paragraphs:
Imperial Moon: Imperial Moon is a BBC Books original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  It features the Fifth Doctor, Turlough, and Kamelion.

State of Change: State of Change is an original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  The novel features the Sixth Doctor and Peri, although the dimensional instability of the realm they are currently visiting causes the Doctor to briefly regress through his first five incarnations; the Sixth Doctor also spends a great deal of time allowing the personality of the Third Doctor to take control of his body when he is forced to fight.

The Eye of the Giant: The Eye of the Giant is an original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  It features the Third Doctor, Liz and UNIT.  It takes place prior to the Missing Adventure "The Scales of Injustice" by Gary Russell.

A Device of Death: A Device of Death is an original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  It features the Fourth Doctor, Sarah and Harry.

The Sorcerer's Apprentice (Doctor Who novel): The Sorcerer's Apprentice is an original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  It features the First Doctor, Susan, Ian and Barbara.

City at World's End: City at World's End is a BBC Books original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  It features the First Doctor, Barbara, Ian, and Susan.

Palace of the Red Sun: Palace of the Red Sun is a BBC Books original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  It features the Sixth Doctor and Peri.

Vanderdeken's Children: Vanderdeken's Children is an original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  It features the Eighth Doctor and Sam.

Shadowmind: Shadowmind is an original novel written by Christopher Bulis and based on the long-running British science fiction television series "Doctor Who".  It was number 16 in the New Adventures and features the Seventh Doctor, Ace and Bernice.  A prelude to the novel, also penned by Bulis, appeared in "Doctor Who Magazine" #202.

First Doctor: The First Doctor is the initial incarnation of the Doctor, the protagonist of the BBC science fiction television series "Doctor Who".  He was portrayed by the actor William Hartnell from 1963 to 1966.  Hartnell reprised the role once, in the tenth anniversary story "The Three Doctors" (1973), although due to his failing health the story was written so he would not have to appear very extensively.

Supporting paragraphs: The Sorcerer's Apprentice (Doctor Who novel) First Doctor
Answer: First Doctor