- You may be looking for Yana (The Stone House).
After the War Master meddled with the Heavenly Paradigm, completely altering the state of the Time War to one that was ultimately more favourable to the Daleks, (AUDIO: The Heavenly Paradigm) he then saw the Dalek Emperor take control of the Time Lords' Cruciform, which frightened him into fleeing from the war. (TV: The Sound of Drums) The Master fled to the far end of time and sent his TARDIS away to Gallifrey without him. He then used a Chameleon Arch to turn himself into a human baby, intending to eventually resume control of his body once the Time War had ended. Speaking to his infant body, the Master's consciousness advised not to cry, telling Yana that one day the people of the universe would need their master. (AUDIO: The Heavenly Paradigm)
Physically human, the rejuvenated Yana was found as a "naked child" on the coast of the Silver Devastation with only an "heirloom" fob watch, which he would carry throughout his life without ever thinking to open it, thanks to a perception filter. As a result of this perception filter on his own watch, he could never keep time and was always late for things.
Being a version of the Master, Professor Yana was plagued throughout his life by the Drumming (TV: Utopia) implanted into the Master's mind as a child (TV: The Sound of Drums) by Rassilon. (TV: The End of Time) However, unlike the Master himself, Yana heard the Drumming in short, overwhelming "spells", rather than a constant, even drumbeat. (TV: Utopia)
Career as scientist
Yana spent his life moving from one refugee ship to another. He had retained the Master's brilliant intellect and became a scientist; this made him invaluable to the scraps of civilisation remaining in the universe at this late stage of its history, as scientists were in short supply. There had not been a university in a thousand years by the time of Yana's "childhood", and the title of Professor, which he took on, was described by him as nothing more than an affectation. Over the years, Yana heard stories about how there was time travel in the old days, but never gave them much credit.
Yana ultimately became responsible for sending the remnants of humanity from their refuge on Malcassairo to Utopia. He became friends with another scientist, Chantho, who was thought to be the last of the native Malmooth race. Together, they worked on the Utopia Project to convey the surviving humans from the planet Malcassairo to Utopia. (TV: Utopia)
Meeting his end
Yana met the Tenth Doctor, Jack Harkness and Martha Jones, who spoke phrases curiously familiar to him, phrases such as Time Vortex, "extermination", Time War, Daleks and regeneration. Martha made the Professor aware of a watch in his possession. Hearing voices in his mind that commanded and entreated him, he opened it and returned to his true identity. After being shot by a dying Chantho, the Master regenerated into his next incarnation shortly thereafter and left behind the form of Yana forever. (TV: Utopia)
The dying Face of Boe warned the Tenth Doctor of the Master's impending return with the last words, "You are not alone", (TV: Gridlock) which the Doctor eventually realised worked out to the acronym "YANA". (TV: Utopia)
Looking back at her various "past faces", and although he was not technically speaking a regeneration of hers, Missy thought of Yana as "the Nice One", to be contrasted with "the Bonkers One" she became after Yana recovered his Time Lord memories. (PROSE: Meet Missy!)
In his human form, Yana was a benign old man who had lost faith in the Utopia project. His spirit was revitalised by the Doctor, and the two shared a mutual admiration. He was also somewhat scatterbrained and slightly lacking in self-confidence, at one point referring to himself as "a stupid old man." Also like the Doctor, Yana could not tell Chantho fancied him much the way Martha fancied the Doctor. He had a deeply compassionite side wishing to help the last of humanity reach Utopia even planning to stay behind on Malcassario and activate the rocket. (TV: Utopia)