The Heretic was a Time Lord who believed that the universe was sick. He planned to regenerate the universe and start fresh.
He created the Cult of the Heretic from individuals of many races to help him. The constructed plans for the Anomaly Cage, which would allow him to activate the universe's renewal using Time Lord biodata. The Heretic was stopped by the Doctor before his plans could be carried out. The Heretic was either killed by the Time Lords or sent to Shada. (AUDIO: The Two Masters)