Professor Elliot was the antagonist in "I Want My Mummy". He sought the Scarabs of Isis in order to gain eternal life and power.
Sam, Clover, Alex and Ian soon discovered, much to their surprise, that the Professor faked his own disappearance instead of being abducted by someone or something else (which was what they initially thought had happened to him).
He had gone to the temple to put the scarabs together and had became invincible. The spies had tried to stop him, but he was invulnerable and had the mummies act on his command. Clover eventually managed to separate the scarabs, and Elliot goes back to normal. He was later arrested by Jerry and two WOOHP agents.
His objective was that of power (which made him different from the other WOOHP villains who usually sought vengeance against those who they felt had wronged them), and he was also one of the few who used the supernatural for his goals.