Rex Lupton (PROSE: Greyhound) was a human from 1970s Earth who, having lost his job when a takeover of the firm he worked for resulted in his redundancy, sought power and revenge over losing his livelihood.
Lupton worked on developing his mental abilities at K'anpo Rimpoche's meditation centre, where he was contacted by one of the Eight Legs of Metebelis III to help them find a blue crystal that the Third Doctor had taken. He was later taken to Metebelis III but the Queen was mistrustful of him from the beginning and he began to turn against the Eight Legs, but was arrested by their guards.
Lupton later insulted the Eight Legs by calling them "superstitious fools", as well as antagonizing the Eight Legs frequently, and they had to use their powers to keep him under control. At a point where Lupton's usefulness to the Eight Legs had come to an end, and when he realized he had lost his one chance to gain power, he lost his temper and referred to the Eight Legs by their true, forbidden name, "spiders", which infuriated them. Lupton then tried to attack the spider who first recruited him, but was killed by a blast of her psychic energy. (TV: Planet of the Spiders) The spiders then headed towards Lupton's corpse and prepared to eat him. (PROSE: Doctor Who and the Planet of the Spiders)