Fan Casting Batman: Shadow of Gotham

Bruce Wayne has been protecting Gotham for two years, as the Batman, within those two years he never faced off against a real supervillain, the worst he had to fight was a mob boss or two, and it was beginning to look like Gotham might not need him. Then suddenly a large string of murders happened, each one having three things in common, the dead bodies were found with a massive grin on it and the cause of death was asphyxiation, any survivors were found to be driven insane and seeing their worst fears, and the police station was mailed riddles before the crimes happened, and soon, Bruce received a riddle as well. Will Bruce crack the case and stop these murders? Or will the criminal or criminals kill all of Gotham, or whatever they are planning?