Dr. Robert Kirk Langstrom hoped to cure his growing deafness by creating a serum that would give him a bat's ability of echolocation. However, the serum robbed him of his intellect and transformed him into a man-sized bat, resulting in a crazed rampage through Gotham City. Langstrom retooled his formula, allowing him to retain his intelligence and is an occasional ally of Batman.

Includes the left arm of Imperiex.