Soldeed

Soldeed was the last surviving scientist of the planet Skonnos. he worked for the Nimons.

Planet
He negotiated an agreement with a Nimon that would give his people the ability to conquer the galaxy. He was utterly devoted to the Nimon and believed wholeheartedly that they would fulfill their part of the agreement and would chastise anyone who would question them. The Nimon trusted only him to enter their presence; anyone else would have been executed.

However, he was disappointed by the Nimon’s refusal to advance him any further technology when the last shipment of sacrifices was lost. When the Doctor and Romana appeared on the scene, he mistrusted them and tried to have them sentenced to death in the Nimon’s complex. Afterwards, the discovery that the Nimon had been lying to him and intended to invade drove him raving mad.

Blaming the Doctor and Romana for interfering, he tried to kill them both as well as reverse everything the Doctor had done to prevent the Nimon from coming through their Black hole. He was shot dead by Seth. (DW: The Horns of Nimon)