Aaron Helzinger was a man who suffered from homicidal rage and was institutionalized in Arkham. When threapy and drugs could not help him they began using experimental surgeries, most notably the removal of his amygdala, the section of his brain that processes emotions and memories. The surgery however only caused him to have even less control over his rage and gave him superstrength. Though generally peaceful, Amygdala can easily be manipulated do to his relatively mindless state, making him a tool for other Batman villains.