During the Uprising, some factions of the Superiors have allied with forces across the multiverse such as the Gendar Infinita, the execrable Lords Dimensional, and even the Adversary's Scion.
When a Superior dies for a final time, they often leave behind an animalistic skeleton larger than their exterior humanoid body. (PROSE: Vignettes of an Uprising)
According to one account, the Master had the appearance of Roger Delgado while on Gallifrey. According to another, he had Anthony Ainley's likeness. According to another one, the one with James Dreyfus's appearance was the incarnation who ran away from Gallifrey.
While fighting to extend his life at the end of his regeneration cycle, many bodies were possessed by the Beevers incarnation, but all kept somehow reverting to his real being until he finally regenerated into the MacQueen one. Hence, these sections cannot be strictly chronological