The Other was one of the three members of the Triumvirate, who founded the Time Lord Society after the cult of Pythia was ended.
The birth and origin of The Other is still a mystery among the Time Lords.
As Rassilon's rule moved closer to despotism and Gallifrey's borders were sealed, the Other attempted to escape the planet by hurling himself into the Looms to await eventual reconsitution.
Some sources imply that he was re-loomed some ten million years later to the House of Lungbarrow as the Time Lord who would become known as the Doctor (NA: Lungbarrow), while other sources imply that the presence of his biodata in the Looms gave rise not to one simple reincarnation but to the wider tendancy for rebellion and discontent that would characterise the Deca's generation of Time Lords (FP: The Book of The War)
A minor Gallifreyan festival known as Otherstide is celebrated yearly in his honour.