Adventure 370 (July 1968) concludes the introduction of Mordru storyline by Jim Shooter and Curt Swan.
Superboy uses his hypnosis machine to erase the Legionnaires memories of their real identities for an hour, correctly assuming that Mordru will search everyone’s minds in his hunt for them. What he doesn’t realize is that Mordru’s magical hunt will alter the effects of the machine, extending the memory loss.
As Mordru takes control of Smallville, Pete Ross realizes Clark must have lot his memory of being Superboy, and goes to Lana for help. She dons her Insect Queen guise, and together they restore Superboy’s memory.
But once the Legionnaires are back in action, they fall to the extremely powerful villain, who puts them on trial, along with Lana and Pete, and imprisons them all in a lead and kryptonite cage.
Or so it seems. Mon-El and Superboy are both puzzled by its lack of effect, and it turns out one of Mordru’s pawns is working against him.
Deception follows deception. Mordru believes he has destroyed Legion headquarters, but that was an illusion cast by Princess Projectra and White Witch, alterted by a vision by Dream Girl.
Mordru’s attempt to destroy Superboy, Mon-El, Duo Damsel, Shadow Lass, Pete Ross and Insect Queen backfires completely as the fireball he creates causes a cave-in, entombing him. And being buried is the only thing that renders Mordru helpless.
A great tale all around, and one of the first Legion stories I read, in the oversize reprint from the 70s.