Vael

Vael Voryunsti Sheverell was the Quantum Theorist of the Time Scaphe.

History
Vael was born to a family of merchants who resided in Soonwell Valley. An Individual, Vael did not adjust well to being set apart from his people and became an embittered and angry young man. He entered the Academia as a Young Hero cadet and studied temporal physics, but didn't fit in. He disliked his fellow cadets and played truant from lectures as often as possible. He failed his final assessments (except for temporal manifold physics) and in a fit of rage accidentally killed fellow student Loie with the full force of his mind. The Pythia, knowing of his power and having foreseen that the next ruler of Gallifrey would be a male, chose Vael as her successor. Although Vael supported the Neo-Technologists, believing he was destined for greatness and wanting to rule Gallifrey, he agreed to be the Pythia's agent.

The Court of Principals made Vael a crew member of the Time Scaphe, replacing the deceased Taspar, but he sabotaged the test flight, sending the time machine out of control. It collided with the Doctor's TARDIS, activating its Banshee Circuits and causing it to reconfigure itself into a multi-dimensional city. After meeting the Seventh Doctor, he realised that the city was his time machine and tried to seize control of it. In an attempt to kill the Doctor, he accidentally turned his power against the egg from which the Process was hatching and destroyed it. Angry and determined to be free of the Pythia, Vael turned his power against himself. (PROSE: Cat's Cradle: Time's Crucible)

In the timeline created by the Process, Vael betrayed his crewmates to the creature, which made them its slaves and Vael its willing servant.