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Marcus Scarman, brother to Laurence, was an English archaeologist and a Fellow of All Souls College, Oxford.
He lived in the same village as Laurence, in a priory that later burned down and the site of which would become that of UNIT HQ. Marcus found the Black Pyramid in Egypt, the prison of the Osiran Sutekh. Sutekh killed him but animated his corpse and used it as a vessel of his power. Scarman (or his body) returned home via a time-space tunnel contained in an
Marcus Scarman receives death after entering Sutekh’s tomb. (Pyramids Of Mars)
Scarman killed Ibrahim Namin, Sutekh‘s servant, and with a small number of Osiran service robots at his command set about doing Sutekh‘s will. He killed his brother Laurence, witnessed the destruction of the Osiran war missile, and travelled to the Pyramid of Mars with a possessed Fourth Doctor and Sarah Jane Smith to release Sutekh from the Eye of Horus.
Despite Sutekh being freed, the Doctor defeated him, after which he relinquished his hold on Scarman’s body, allowing him to die. Scarman appeared to regain his personal consciousness, saying “I’m free! Free at last…”, in the moments before he collapsed, died and turned to dust. (Pyramids Of Mars)