Number Thirteen

I.M. Foreman was a Gallifreyan monk who lived on Gallifrey but was driven from the monasteries following Rassilon's Intuitive Revolution.

Biography
Having been exiled to the wilderness after the dissolution of the old religious orders, I.M. Foreman found twelve individuals, all of whom had no memory of who they were, but who they eventually deduced were his future twelve incarnations. Together they formed I.M. Foreman's One-Species Nongenetically Engineered Travelling Show, a show which was actually a complex space time event that could travel in Time. As a priest, he had been given the gift of regeneration, but in those days it was much less stable than modern regeneration, meaning he tended to absorb the DNA of whatever he encountered in his life whenever he regenerated, each of his incarnations being increasingly less human as they moved on from his original body.

He eventually arrived on Dust, where his true nature was revealed to the Third Doctor and Sarah Jane Smith. I.M. Foreman's travelling show was made up of thirteen acts, which were all aspects/bodies of I.M. Foreman, one for each regeneration. When the Remote attacked the planet, they let out Number 13, the most unstable of all his regenerations, which tried to eat everything and absorb it into its own structure. After it consumed the attacking Faction Paradox fleet, the Doctor was able to convince it to blend with the planet Dust to turn it into a new, vital world. With the crisis concluded as the planet grew more vibrant, Foreman's consciousness formed a bond with a woman called Magdalena to allow him/her/it to experience the world as its residents would.

The other regeneration aspects were sent back through time thanks to the Doctor linking the show to the TARDIS and sending it back to Gallifrey. Arriving at its destination with no arrival site prepared for it, their travelling show exploding as it ended up back in the Dark Times just before the first I.M. Foreman found the show, triggering a regeneration for all twelve aspects, each of them changing into their next self while losing their memories due to the trauma of the damage and the limitations of their current ability to regenerate. (PROSE: Interference - Book Two)

I.M. Foreman was registered as the scrap merchant owner of the scrapyard at 76 Totter's Lane, where the First Doctor hid when he ran away from Gallifrey with his granddaughter in his stolen TARDIS. (TV: An Unearthly Child, Attack of the Cybermen, The Day of the Doctor )