Mason Harding was an American scientist who was kidnapped by the royalist organization known as “The Elite” and coerced to build the Madbomb, a device that drove its subjects to mass hysteria. He initially aided The Elite willingly, as he needed money for his daughter Carol’s medical treatments, but when he grew aware of their intentions to enslave the U.S. populace using his technology, he was forced to finish the device in spite of his objections. He was imprisoned when The Elite’s plot was foiled by Captain America and the Falcon.
Later, Harding accidentally nullified the effects of Captain America’s Super-Serum while trying reverse the effects of Cap’s memory loss.