A. St. John D. Caldera

Professor A. St. John D. Caldera was a neurologist whose mind was stolen by Skagra at the Think Tank space station. He died in the destruction of the station. (TV: Shada)

However, Caldera's mind lived on in the Sphere. After the Doctor defeated Skagra, he took the Sphere to Drornid, where he had the minds of Caldera and the other victims of the Sphere transplanted into new bodies. (PROSE: Shada)