Nicholas Valentine is the main antagonist of the Doctor Who audio play "Phantasmagoria".
He was voiced by the late David Ryall.
Known on Earth as Sir Nicholas Valentine, his true identity was Karthok of Daeoladus, an alien war criminal who had slaughtered thousands in his experiments. He fled justice but crashlanded on Earth. Since his ship was largely biological in nature, it was capable of healing itself but required brain power. To this end, every thirty years, Valentine emerged in order to kidnap intelligent young men and harness their intelligence, burning them out in the process.
By the early 18th century, Valentine was attending the Diabolus Club in London, using card games to find out who had the right level of intelligence. His cards were treated to absorb the bio-data of anyone who touched them, acting as a homing beacon and allowing him to abduct them with the spirits of his previous victims. Valentine himself wore gloves while playing to avoid touching the cards himself.
Valentine's activities drew the attention of the Doctor, who witnessed a man die of heart failure as the result of an abduction attempt. Valentine in turn was intrigued by the Doctor, wondering if he possessed enough intelligence to be the controlling brain for his nearly-repaired spaceship, which he was intending to launch from below London, destroying most of the city in the process. He tried to trap the Doctor by giving him one of the cards but the Doctor managed to destroy it.
The daughter of two of Valentine's victims had followed him to Earth, taking on the identity of a serving girl named Hannah, and accompanied the Doctor in tracking Valentine to his base. However, with the whole ship obeying him and equipped with defensive weapons, Valentine still had the upper hand and plugged Hannah into his machinery. The Doctor however tricked Valentine into touching one of the cards, making him a target for the spirits. Although it cost her her life, Hannah urged Valentine's other victims to turn their psionic force against Valentine, killing him.