Dark Design

The Dark Design was a medical condition that certain Time Lords suffered from when they went mad. When this occurred, the Time Lord began to suffer from a storm across the surface of their brains. Those that suffered from this condition on Gallifrey were hidden away in institutions. (NA: Falls the Shadow)

Many inventive and brilliant Time Lords become corrupt and insane, which caused the condition of the Dark Design. Sufferers included Rassilon (BFA: Zagreus), Omega (DW: The Three Doctors), Morbius (DW:The Brain of Morbius) and Borusa (DW: The Five Doctors).

When Omega fought the Third Doctor in the anti-matter universe, he said he fought with the "dark side of his mind" and he was insane. This may have been the Dark Design (DW: The Three Doctors).