Chief Sea Devil (The Sea Devils)
A Chief Sea Devil led the Sea Devils who awoke in the 1970s. After his death, the Master said he had been "one of the most intelligent creatures that ever walked on this Earth".
Like many of his people, the Chief Sea Devil spent millennia in hibernation. He woke up in an unfamiliar Earth dominated by humans in the 1970s due to an oil rig's activities. The renegade Time Lord known as the Master 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. (TV: The Sea Devils, PROSE: Doctor Who and the Sea-Devils)
According to one account, this Chief Sea Devil was killed by Myers. Thereafter, a new Chief Sea Devil took over, and refused to honour his predecessor's agreement with the Master. (PROSE: Doctor Who and the Sea-Devils) According to another account, it was the same Chief Sea Devil who turned on the Master. (TV: The Sea Devils) Ultimately, the whole Sea Devil colony was killed by the device which the Master had built to awaken those still in hibernation, which the Doctor had rigged to explode instead. (TV: The Sea Devils, PROSE: Doctor Who and the Sea-Devils)