I.M. Foreman was a Gallifreyan monk who lived on Gallifrey but was driven from the monasteries following Rassilon's Intuitive Revolution.
Biography
In the wilderness, I.M. Foreman found twelve individuals, all of whom had no memory of who they were. 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.
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. Eventually it blended with the planet Dust to turn it into a new, vital world, Foreman's consciousness forming 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, 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. (PROSE: Interference - Book Two)
I.M. Foreman is registered as the scrap merchant owner of the scrapyard at 76 Totter's Lane, where the Doctor hides when he runs away from Gallifrey with his granddaughter in his stolen TARDIS. (TV: An Unearthly Child, Attack of the Cybermen, The Day of The Doctor )