Grandfather Paradox

Grandfather Paradox was the nominal leader of Faction Paradox.

Biography
When the Grandfather was in his youth, he travelled back in time into his own past and used an ordinary knife to murder his own grandfather. The paradox of this caused the Grandfather to be simultaneously alive and dead — murderer and victim. (PROSE: The Gallifrey Chronicles)

Called the "voodoo priest of the House of Lungbarrow", Grandfather Paradox was imprisoned in Shada after founding House Paradox and buying the Eleven-Day Empire. Popular fable maintained that he was imprisoned rather than executed because "everyone was more afraid of him dead than alive". When the Carnival Queen threatened rationality throughout the universe, Lady President Romana released three hundred prisoners, including the Grandfather, during an epileptic fit. (PROSE: Christmas on a Rational Planet) He later cut off the arm that held the Time Lord prisoner tattoo. (PROSE: Interference - Book One)

After escaping prison, he remade House Paradox into Faction Paradox, creating beliefs and rituals for the Faction meant to specifically torment the Great Houses of the Time Lords, including the symbolism of magic, paradoxes, and "base physicality" (hence the blood masks and the "family members" ranking policy). He later wrote himself out of history as a final insult, leaving Faction Paradox as his legacy and a constant thorn in the side of the Great Houses. (PROSE: The Book of the War) The speaker's chair in the Eleven-Day Empire was left perpetually vacant to be taken by the Grandfather upon his appearance to the Faction Paradox. (PROSE: Interference - Book One)

Resulting from a corrupted timeline where the Third Doctor was infected with a Faction Paradox biodata virus after he regenerated ahead of schedule on the planet Dust, a future version of the Eighth Doctor modelled himself as the Grandfather Paradox; in this iteration, the Grandfather was a bald man with a stump in place of his left arm wearing black armour and robes, described by Fitz Kreiner as resembling the Doctor "if he'd spent twenty years in the navy before becoming a psycho". However, this timeline was still uncertain even when the Grandfather appeared to confront the Doctor, as the Doctor's TARDIS had contained the infected timeline in itself, resulting in both timelines and versions of the Third Doctor's regeneration being potentially 'real'. This continued until the Doctor drained the TARDIS's power, forcing the universe to 'choose' only one of the two timelines it was containing to become 'real', with the result that reality returned to the timeline where the Third Doctor never even went to Dust and was thus never infected, erasing the Faction and the Grandfather from existence. (PROSE: The Ancestor Cell) However, other accounts suggested that Grandfather Paradox appears as a twisted, morally bankrupt and broken version of whoever is looking at him or "the ghost of Christmas cancelled" as the Doctor snidely put it. (PROSE: The Gallifrey Chronicles)

During the War, Cousin Justine possessed the shadow of the Grandfather, which made her accountable to the Great Houses for all of his crimes (since Faction Paradox law states the shadow is more important than the person). This, coupled with the alliance signed between the Houses and the Faction, gave Lolita and the Houses the excuse they needed to destroy the Empire. (AUDIO: The Eleven Day Empire) Cousin Shuncucker also held the Grandfather's shadow. (AUDIO: Movers)

Behind the scenes

 * The name Grandfather Paradox punningly refers to the familiar time travel concept from theoretical science and science fiction.
 * Lawrence Miles intended Grandfather Paradox to never actually appear, similar to the Doctor's true name or Judge Dredd's face.