Drang was the leader of the chrononauts of Aoris in Era 24. He thought that the Fourth Doctor was from his planet's past. He then asked the Doctor to deactivate a bomb. (AUDIO: The Paradox Planet)
He recaptured the Doctor and executed Embery. The Doctor told him that he was the cause of all of the problems that Aoris had suffered, as his attacks on the past had created a time loop where the past civilisations would be deprived of key resources and thus create his future. He realised that he had to stop the war and he could rewrite history but the Doctor told him how catastrophic this would be. After his efforts failed, he committed suicide by allowing himself to be consumed by one of the rare animals he had saved from the past. (AUDIO: Legacy of Death)