One of Captain Marvel's primary villains, Mister Mind is a two-inch alien worm of high intelligence. Mind usually carries out his villainous plans through an organization called the Monster Society of Evil, significant as the first supervillain team in comics to contain villains that a hero had fought previously; prior to this, supervillain teams were composed of villains created just for that storyline. The Monster Society made its debut in Captain Marvel Adventures #22, and the resulting "Monster Society of Evil" story arc continued for two years in Captain Marvel Adventures, ending with issue #46.