E is for... Eldrad

A scientist of the Kastrian race. He provided his people with special barriers which protected their world from freezing cosmic storms, as well as a silicon-based body pattern. He grew overly ambitious - seeking to take over the planet and lead it on a crusade of galactic conquest. When this was denied him, he destroyed the protective barriers. If he could not rule, then no-one would. He was captured by forces loyal to King Rokon and sentenced to obliteration. Placed in a space capsule he was launched into deep space. As life on the surface of Kastria became impossible, the capsule was blown up prematurely, with a small chance that Eldrad might survive.
Millions of years later, Sarah Jane Smith was caught up in a blasting accident in an English quarry. When found, she was clutching Eldrad's stone hand. The Doctor discovered that the hand could absorb radiation to regenerate itself. The hand possessed a blue crystal ring, which could exert hypnotic powers over humans. It compelled Sarah to take the hand to a nearby nuclear power plant where it could regenerate itself fully. The ring manipulated other people to help Sarah achieve this.
Eldrad absorbed the full output of the nuclear reactor, and was able to use his powers to neutralise an attack from atomic weapons. He regenerated into a female form - based on the person with whom he had last had contact - Sarah.

Eldrad claimed to have been executed after her planet was invaded by an enemy race. She asked the Doctor to take her home to Kastria. To protect the Earth, he obliged, but insisted that it be the Kastria of the present day. Back on her homeworld, Eldrad was shot by a booby-trap - a dart filled with an acid which attacked silicon lifeforms. She had the Doctor and Sarah take her to the lower levels where there was a regeneration chamber. Her body was destroyed, but she was regenerated as her natural, male form - the blue crystal ring holding his genetic code. The Doctor and Sarah discovered the truth about him when an ancient recording of King Rokon was activated. Eldrad discovered that his people had chosen extinction over his possible return to rule over them as a tyrant. Eldrad then decided to return to Earth and conquer that world, but the Doctor tripped him up and caused him to plunge into a deep chasm. He suspected that Eldrad might survive the fall, but would be left as ruler of a dead world.

Played by: Judith Paris and Stephen Thorne. Appearances: The Hand of Fear (1976).

• Thorne had previously played the Daemon Azal, and the Time Lord Omega, as well as one of the principal Ogrons in Frontier in Space.