With his mental strength and rigorous training, Batman is the solitary hero who protects Gotham. However, the villains threatening Gotham's safety are becoming more ruthless by the day. A conflict over justice also arises with the shining hero of Metropolis, Clark Kent, aka Superman, prompting Batman to build a massive device without revealing its purpose. Firefly, Killer Croc, the Riddler, Deathstroke, Joker... more and more supervillains are emerging.