Morestran

Morestrans were humans who had colonised the planet Morestra, and had then built a space-faring empire which spanned eighty million light-years.

History
When their homeworld's star began to die, Morestra's scientists began searching for new energy sources. Sorenson led an expedition to the planet Zeta Minor, where he hoped to harness the power of the anti-matter he had discovered there. The other members of his team were killed, along with much of the crew of the ship sent to rescue them, until the Fourth Doctor saved them by returning the anti-matter to the planet. He then suggested to Sorenson the idea of harnessing the kinetic power of planetary movement. (TV: Planet of Evil)

This, however, corrupted the Morestrans and sent them up a technological cul-de-sac. (PROSE: Zeta Major)