The General

Kenossium, commonly referred to as simply the General, was a General in the Time Lord military.

Early days
The General was, for their first ten incarnations, a woman. (TV: Hell Bent) Like all Time Lords, she was taken from her family at the age of eight for the selection process in the Drylands. Staring into the Untempered Schism as part of a Time Lord initiation rite, she was inspired by what she saw in the Schism. (PROSE: A Brief History of Time Lords)

At the Time Lord Academy, Kenossium was mentored by Bellator, whose lessons taught her how to survive "sixteen transwarp campaigns and a Time War." (COMIC: The Clockwise War) She was a Prydonian and was top of her class for temporal stratagem despite being "an unruly young woman" at the time. (AUDIO: Remnants)

They became the Time Lords' military commander, (TV: Hell Bent) adopting "the General" not only as their rank, but as their primary name. (TV: The Day of the Doctor) The General was present on Gallifrey when the First Doctor stole a TARDIS and witnessed the commotion caused by the event. (PROSE: The Day of the Doctor)

The General's incarnations
The General's tenth regeneration resulted in a male eleventh incarnation. He appeared as a grey-eyed middle-aged light-skinned bald man. (TV: The Day of the Doctor, PROSE: Lords and Masters)

After the Twelfth Doctor shot him, the General regenerated into their twelfth body, this time having the form of a dark-skinned woman with a shaven head. (TV: Hell Bent)

Later life
Many years after the conclusion of the Time War, the General would deny that additional Doctors other than the war, tenth and eleventh incarnations were present in the saving of Gallifrey. (PROSE: A Brief History of Time Lords)

Behind the scenes

 * The General's regeneration in Hell Bent marked the first time since The Curse of Fatal Death a gender-swapped regeneration was shown on television.
 * Incidentally, it was also the first regeneration witnessed in the revived series where the Time Lord in question was lying down, rather than standing up, and the regeneration was far calmer than is generally seen with Time Lords such as the Doctor and.
 * According to TARDIS Type 40 Instruction Manual, the General wrote an unofficial memoir titled "Thirteen of Them: I Didn't Know When I Was Well Off", which detailed the events at the climax of the Last Great Time War.
 * Following the revelation in Hell Bent that all of the General's regenerations prior to the Ken Bones incarnation had been female, a fan theory emerged that "the General" was a new identity adopted by Romana at the end of the Last Great Time War. Although contradicted by a handful of sources (most notably The Clockwise War giving the General a different birth name from "Romanadvoratrelundar", and the Twelfth Doctor Doctor Who Experience Interactive Story depicting Romana still in her Lalla Ward incarnation in "the very last days of Gallifrey"), this idea was endorsed by veteran Doctor Who writer Jonathan Morris, who indicated in 2020 that he intended to confirm it in a licensed short story at the first opportunity.
 * The General was the first case of a distinct Time Lord being introduced as using the same "the" title as another, earlier Time Lord despite the two having no known relationship; prior to the Ken Bones General's introduction, the novel Warmonger by Terrance Dicks had seen Morbius adopt the name of "the General" following his exile from Gallifrey (although as shown in The Brain of Morbius, he would late revert to his birth name after the failure of his galactic war).