The Mad Hatter is one of Batman's enemies. He is psychotic and has an obsessive-compulsive disorder. His main weapons are mind controlling devices.
He is one of Talia al Ghul's henchmen. Tetch has once used his abilities to shape the previously empty mind of Heretic (a clone of Damian Wayne) into a perfect soldier for his master's organization the League of Assassins. After Batman is captured by the Heretic and taken into their headquarters, the Mad Hatter reprograms his brain into devotedly following Talia al Ghul's orders and revealing all of his and his allies' secrets. With Batman's help, the League of Assassins infiltrates the World Tech Summit in Gotham hosted by Bruce Wayne and takes over Wayne Enterprises' technologies. Tetch starts to brainwash all the attending politicians and dignitaries into obeying Talia. However, he is killed by a system overload caused in the ensuing battle between Batman's allies and Talia's henchmen halting the process. The overload causes his head to explode.