The Clock People were a race who lived in the time vortex.
The Clock People granted individuals the ability to alter their pasts by correcting mistakes. People who accepted had their timelines erased, since it unravelled their personal history. This allowed the Clock People to take their physical place. (PROSE: Anachrophobia)
The Clock People evacuated the time vortex because of the Council of Eight. They were dependent on the breach in the Time Vortex created by Payterson's experiments, which served as their lifeline. They were wiped out when the Eighth Doctor sealed the breach. (PROSE: Anachrophobia)