Voord

The Voord were a race of beings who had discovered how to resist the Conscience Machine on the planet Marinus.

History
The Voord, led by Yartek, sought to take control of the Conscience Machine, thus taking control of the planet, but were defeated by the Doctor and his companions. (DW: The Keys of Marinus)

The Voords began experimenting with a World Shaper which came from a spacefaring civilization to accelerate time locally and "quick-evolve" themselves. Over time they replaced there body parts with cybernetic parts. The Doctor, Frobisher, Peri Brown and Jamie McCrimmon attempted to stop the Voord. Jamie sacrificed himself to destroy the World Shaper, this caused a blast that accelerated time so much that Marius that became known as Mondas and the Voord evolved into entirely Cybernetc creatures called Cybermen. (DWM: The World Shapers).


 * This last account conflicts with other accounts of the origin of the Cybermen.