Rex Lupton (PROSE: The Brigadier's Memoirs) 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.
He worked on developing his mental abilities at K'anpo Rimpoche's meditation centre, where he was contacted by one 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 "spiders" — the use of which the Eight Legs had forbidden. He also antagonised the Eight Legs frequently, and they had to use their powers to keep him under control. At a point where his usefulness to the Eight Legs had come to an end, and when he realised he had lost his one chance to gain power, he tried to attack the spider who first recruited him but she killed Lupton before he could strike her. (TV: Planet of the Spiders)