Who Is Mephisto? Agatha All Along Calls Back to a Popular WandaVision Fan Theory
In the comics, Mephisto is strongly connected to the mystical side of the Marvel universe, though he has had tousles with other characters. In Avengers West Coast #51, Wanda uses part of Mephisto’s soul to give birth to her sons Billy and Tommy, which is obviously something he doesn’t take too kindly to and eventually reabsorbs them.