Thea Ransome was one of a team of scientists and technicians working for Dr Fendelman in Fetchborough.
Biography
They were investigating the enigma of "Eustace", an apparently human skull which had existed eight million years before archaeology had estimated humans had evolved. In actuallty, they had found not a human skull, but the remnants of a dormant Fendahl Core.
Taking her prisoner and making her part of a ritual in July 1977, her co-worker Maximillian Stael and his coven used Eustace to transform Ransome into another Fendahl Core. In this form, she appeared as a golden skinned, majestic, unblinking maiden who could induce paralysis with a glance and transform humans into Fendahleen. (TV: Image of the Fendahl)