Borusa (The Five Doctors)

Borusa was a Time Lord who held the office of Lord President.

Death Zone scheme
Having regenerated due to the sheer stress that the office of Lord President entailed — (PROSE: The Legacy of Gallifrey) with his stubborn streak apparently enhanced in the process — Borusa used his presidential powers to investigate the legacy of Rassilon from the Dark Time of Gallifrey. He pursued access to the Tomb of Rassilon, where he believed he would find the secret of immortality, ruling Gallifrey forever as "President Eternal". To this end, he reactivated the ancient Time Scoop and revived the long-forbidden war games between captured representatives of various species in the Death Zone surrounding the Tomb.

Borusa summoned all of the Doctor's previous incarnations to the Zone (though the Fourth Doctor ended up becoming trapped in the Time Vortex), convinced that at least one would gain entry to the Tomb. He also arranged for the Master to be sent into the Death Zone- officially to help the Doctor but unofficially to 'inspire' the Doctor by giving him a clearer villain to face- and time-scooped at least one Dalek, one Robot Yeti, and a squad of Cybermen to go into the Zone as well. Although the Fifth Doctor was sent to the Capitol and managed to learn what Borusa was doing despite his attempts to frame other parties, Borusa used the Coronet of Rassilon to take control of the Fifth Doctor once the first three Doctors had reached Rassilon's tomb and been tricked into deactivating the forcefield blocking transmat access to the Tomb. After reaching the Tomb, Borusa used the Coronet to paralyse the Doctors' assembled companions, but the first three Doctors were able to link minds to free their fifth self, the four Doctors joining together to stand against Borusa. As an avatar of the Matrix Rassilon appeared in the tomb, he offered Borusa immortality, but as the First Doctor had realised, the promised immortality was a trap set by Rassilon to capture power-mongers such as himself. Borusa was condemned, like others before him, to live his "immortal" life trapped within a sarcophagus. (TV: The Five Doctors)

Later fates
Two similar yet contradictory accounts showed Borusa being freed from the Tomb and redeemed. By one account, Borusa's former supporter Rath allied with the vampire Agonal to break into the Tomb and free Borusa while killing Rassilon. Made flesh again with a Time Gun, Borusa showed regret for his actions and borrowed Rassilon's mental power to destroy Agonal. After a tender moment with the Seventh Doctor, Borusa vanished as Rassilon took him to "a better place". (PROSE: Blood Harvest) In another version of history, the Eighth Doctor freed Borusa from the Tomb during the Sixth Doctor's trial. Because this incarnation of Borusa had been a megalomaniac fluke, Rassilon reverted Borusa to a previous incarnation. (PROSE: The Eight Doctors)

By other accounts, Borusa remained trapped in the Tomb of Rassilon until the Last Great Time War. Rassilon repurposed him into the possibility engine. (PROSE: Engines of War)

Appearance
This incarnation of Borusa was again an older man. (TV: The Five Doctors) He had a long, intellectual face. (PROSE: The Five Doctors)