Eldrad

Eldrad was a Kastrian overlord who was sentenced to death and obliterated.

Biography
150 million years before the 20th century, Eldrad was a brilliant scientist who created a barrier to protect Kastria from the solar winds and new, silicon-based bodies to deal with the environment. He planned to make his people, the Kastrians, into aggressors, which caused a revolt. These Kastrians, led by King Rokon, captured him and placed him in an obliteration module detonated by remote control. Though he was almost entirely destroyed, one of his hands and his ring survived and somehow made it to primordial Earth.

Eldrad's damaged and petrified hand was found in an English quarry just before it was blown up. Having just arrived on Earth in the TARDIS with the Fourth Doctor, Sarah Jane Smith was caught in the blast and found the hand. Eldrad's ring took control of her mind, forcing her to go to the nearby Nunton Experimental Complex, which had a nuclear reactor.

Though the Doctor saved Sarah from Eldrad's powers, the ring influenced Dr. Carter and Driscoll, who also tried to help Eldrad regenerate. Eldrad made Driscoll take his hand into the core of the reactor. Eldrad employed the reactor's radiation to completely regenerate into a form modelled on Sarah, the ring having taken her imprint.

Eldrad claimed she had been overthrown after a war between her people and another and asked to be brought back to her homeworld. The Doctor agreed to take Eldrad to Kastria, but refused to go into to the past. Eldrad led the TARDIS to Kastria. In the Kastrian base, Eldrad was poisoned by an acid harpoon, which started to break down her system, though she reached a regeneration chamber before her structure broke down.

Restored to his true Kastrian form, Eldrad planned to take back Kastria and then the universe until he learnt of the fate of the Kastrians, who, led by Rokon, had chosen suicide rather than facing the small chance of Eldrad returning to lead them. Eldrad decided to return to Earth in the TARDIS and enslave it.

The Doctor stole Eldrad's ring and tried to escape with it. Chasing the Doctor, Eldrad tripped over his scarf and into a deep chasm. Though Eldrad now seemed to have died, the Doctor expressed doubt about his demise. (DW: The Hand of Fear)

Powers and Abilities
Apart from the abilities as regeneration and metamorphosis granted him by his silicon-based form, Eldrad could use telepathy and attempted to hypnotize the Doctor. When he did so, his eyes glowed bright blue. (DW: The Hand of Fear)