Magnus

Magnus was, by several accounts, a Time Lord and friend of the Doctor during their early life at the Time Lord Academy, who later adopted the role of the War Chief.

Some accounts implied Magnus went on to become the Master, (COMIC: Flashback, PROSE: Invasion of the Cat-People, Goth Opera) of whom, by some accounts, the War Chief was an incarnation. (PROSE: Doctor Who and the Doomsday Weapon) Other accounts stated that the War Chief was an incarnation of Magnus distinct, but Magnus was distinct from Koschei, the Master. (PROSE: Divided Loyalties)

Early life
In an account which did not use the name of "Magnus" but seemed to treat the War Chief as distinct from the Master, and which did not precisely identify the incarnation(s) he inhabited during these events, as a young Time Lord, the War Chief began to rise rapidly in the Time Lord hierarchy, (PROSE: Timewyrm: Exodus) becoming a member of the High Council. (PROSE: The Legacy of Gallifrey) The warmongering Time Lord's social climbing caused Cardinal Borusa to see him as a threat to his own position of power, so he persuaded the Celestial Intervention Agency to manufacture evidence of treason against him. Believed to be a criminal, the War Chief fled from Gallifrey, became a renegade, and swore revenge on the Time Lords. (PROSE: Timewyrm: Exodus) The Celestial Intervention Agency had little information about the War Chief; they believed that he had indeed been implicated in the Prydonian Academy Revolution and had fled Gallifrey thereafter, in a Type 42 TARDIS. (PROSE: CIA File Extracts)

Magnus's incarnation
Magnus was careless with his regenerations, having already changed multiple times when his friend the Doctor was still in his first body; (COMIC: Flashback) the Second Doctor recalled advising Magnus to be more careful with his regenerations and being ignored. (PROSE: Invasion of the Cat-People)

Magnus and the War Chief as documented in some accounts (COMIC: Flashback, PROSE: Invasion of the Cat-People, TV: The War Games) may have been incarnations of the Master rather than a distinct Time Lord; many subsequent incarnations of "the Master" were documented by other sources, (PROSE: Doctor Who and the Doomsday Weapon, etc.) having, after the War Games incident and his regeneration, adopted the new moniker of "the Master" instead of earlier titles and designations. (PROSE: Doctor Who and the Doomsday Weapon, Doctor Who and the Terror of the Autons)


 * According to one account, in his first incarnation, Magnus was a member of the Deca separate from Koschei. After the escapade during which the Deca met the Toymaker, he evaded scandal and got himself "assigned to the scientific research department for the rest of his time at the Academy". (PROSE: Divided Loyalties)
 * A Magnus who was no longer in his first incarnation sought to exploit an energy creature from the Time Vortex as a source of energy to gain the respect of his fellow Time Lords. Despite their earlier friendship, the First Doctor put an end to the plot when he learned of it, viewing it as unethical. This was the start of the long-standing enmity between the two. (COMIC: Flashback)
 * When the War Lord met his future War Chief in a "Trastevarian jail", he was dying, and ended up regenerating in front of the War Lord. (PROSE: Save Yourself)
 * In a body with Multiple accounts suggested this man was an incarnation of the same man who later became "the Master", (AUDIO: The Home Guard, PROSE: Doctor Who and the Doomsday Weapon, etc.) although others claimed that "the War Chief" was a distinct Time Lord. (PROSE: Divided Loyalties, A Brief History of Time Lords)
 * After his botched execution, the War Chief attempted to regenerate and ended up trapped in a monstrous, two-formed intermediate form when the regeneration went wrong. Under the alias of Felix Kriegslieter, this version of the War Chief infiltrated the Nazi Party on behalf of the War Lords until the plot was derailed by the Seventh Doctor. The account describing Kriegslieter did not seem to account for the War Chief having been an incarnation of the Master, though it did not use the name of "Magnus". (PROSE: Timewyrm: Exodus)

Other references
Ruath described "that idiot Magnus" as one of four notable renegades, alongside the Doctor, Mortimus, and the Rani, who had studied together under Borusa. (PROSE: Goth Opera)

When the Seventh Doctor broke into the Monk's TARDIS, the Monk initially assumed it was Magnus come to steal the Monk's gold. (PROSE: No Future)

Behind the scenes
The name of "Magnus" was first used in Flashback for a character intended to be an early incarnation of the Master. In Invasion of the Cat-People, Gary Russell referenced the character under the same assumption, noting that the Doctor had once fruitlessly advised Magnus to be careful with his regenerations, tying in with the idea of the Master having burnt through his original regeneration cycle at an accelerated rate to later end up as the Decayed Master. In Goth Opera, Ruath lists the Doctor's fellow students at the Academy under Borusa to have later become "scoundrels": "Mortimus, the Rani, that idiot Magnus… and you, Doctor", very directly acknowledging the idea of Magnus being the Master, as it would be unthinkable for such a list not to include the Master. All this did not mean he was not also an early version of Edward Brayshaw's War Chief as seen in The War Games, with multiple early sources having embraced the idea that the War Chief was himself a pre-Delgado incarnation of the Master.

However, Terrance Dicks's Timewyrm: Exodus showed a partially regenerated version of "the War Chief" encountering the Seventh Doctor with no apparent awareness on the Seventh Doctor's part of having met this Time Lord since The War Games. Now taking it as read that the War Chief was not an incarnation of the Master, Russell's Divided Loyalties, having contradicted the idea that the War Chief seen in The War Games was an incarnation of the Master, Gary Russell instead "Magnus" as being the name of a distinct Time Lord of whom the War Chief was an incarnation, as was the Flashback Time Lord, while Delgado's Master onwards were not.