Rann-Korr was a Hyperion.
After a war with the Time Lords which ended in the 15th century, the Hyperions were destroyed. A survivor, Rann-Korr, remained in suspended animation below the surface of Isen VI. It was awoken in the 25th century by terraforming equipment. It planned to restore its race and try to conquer the universe again. It was stopped by the Twelfth Doctor, who channeled the seas of the planet into the caverns where Rann-Korr had been hibernating. This cooled and killed it. (COMIC: Terrorformer)