Like some of his people, the Chief Sea Devil slept for millennia. He woke up in an unfamiliar Earth dominated by humans. The renegade Time Lord known as persuaded him to help destroy the human race. The Third Doctor argued for peace and offered to broker a deal between the two species. The Chief agreed to this but the agreement was soon demolished when Walker, the human politician in charge of the situation, ordered Captain John Hart to launch an attack on the Sea Devils' base. Subsequently the Chief Sea Devil repudiated his agreement with the Doctor and helped the Master who (with the Doctor's "assistance") constructed a device designed to wake the rest of the Sea Devils. The Doctor rigged the device to explode and destroy the Sea Devils' base. The Chief Sea Devil, along with all of the o