Originally Posted by tingramretro:
“The Master apparently used up all his regenerations off screen; the Ainley and Eric Roberts Masters were not true regenerations but the dying Master possessing the bodies of other people to artificially extend his life. He was eventually seemingly resurrected and given a whole new regeneration cycle by the Time Lords. As for the Castellan; three individuals using that title have been seen on screen, Castellan Spandrell (who it's indicated is not actually a Time Lord; though he's certainly a Gallifreyan, he seems to know little about the workings of Time Lord biology), Castellan Kelner and the unnamed Castellan seen in Arc of Infinity and The Five Doctors. The word 'Castellan' is not a name, but the title given to the keeper of a citadel-on Gallifrey, it seems to roughly equate to the Capitol's Chief of Police.”
Is the jury still out as to whether the Delgado Master was the last 'true' incarnation before his decay seen in The Deadly Assassin?
I ask because when the 3rd Doctor encounters the Ainley Master in The Five Doctors, he says 'another regeneration...' to which the Master says 'not exactly'. To me this suggests the Doctor either didn't know the Delgado Master was in his final incarnation or there were subsequent incarnations between Frontier in Space and The Deadly Assassin.