Dynamo Boy is an alias employed by a dark-haired evil youth named Vorm, a pirate from Darzyl. Possessing no super-powers, he uses a multi-functional power belt to fool the Legion of Super-Heroes into admitting him as a member. By spinning lies and deceptions (with some psychic help from Saturn Queen), he makes accusations that turn the Legionnaires against each other. The Legion's members are finally all expelled, leaving Dynamo Boy as the only remaining member (Adv No. 330/1, Mar 1965: "The Secret of the Mystery Legionnaire!").
Dynamo Boy interviews new candidates who he hopes will help him in his plans to plunder loot from citizens. The recruits either are too "good" (Animal Lad) as determined by Vorm's belt that can read "auras" or are hopeless and inept like Polecat (a boy with a super-powerful odor) and Tusker (a teen with uncontrollably-growing canine teeth). Eventually, Dynamo Boy simply relaxes the age requirements of the Legion and inducts the Legion of Super-Villains. The Villains turn on the boastful Vorm and strand him on a dead Earth in the most distant possible future. It is left for Superboy and two previous Legionnaires to defeat the Super-Villains and restore the original Legion (Adv No. 331/1, Apr 1965: "The Triumph of the Legion of Super-Villains!").