According to Coordinator Engin, in his own time Rassilon was chiefly regarded as an engineer and architect. (TV: The Deadly Assassin) Rassilon ended the Dark Time and the matriarchal society of the Pythia. In retaliation, the wrathful Pythia cursed her enemies and made Gallifreyans sterile. (PROSE: Cat's Cradle: Time's Crucible)