Mesmero was a small time crook who posed as a stage hypnotist at high society parties. He used his mutant powers to mesmerize guests into giving him their possessions and then making them forget about them. Mesmero later took control of large numbers of latent mutants, and captured Lorna Dane.
Mesmero and his androids placed Lorna inside a genetic stimulator, which altered her genetic structure to allow her to exercise her latent powers. Mesmero then used his hypnosis on Lorna to alter her personality so that she would sympathize with a faux Magneto and believe him to be her father.
Mesmero later dropped his control over Lorna, assuming that she would obey her supposed father unquestioningly. However, after it was revealed to her that Magneto was not her father, Lorna assisted the the X-Men in defeating the villains.
The Birth of M-2
"City of Mutants"
Art by Jim Steranko