Hannibal Bates was a former convict who was employed by Lex Luthor to participate in the Everyman Project, a secret LexCorp experiment to allow its subjects to shape-shift. Hannibal would emerge the only survivor of these experiments, taking on the moniker of Everyman.
Since the aftermath of Conduit's Attack on Metropolis, Luthor has employed Bates to help a number of captured criminals and Metahuman's escape captivity and recruit them to Luthor's side.