Most recently, in Gotham City Sirens #1, Poison Ivy is controlling the Riddler, keeping him in a nearly vegetative state so she and Harley Quinn can move into his townhouse and use it as a hideout. When a villain named Boneblaster decides to make a name for himself by killing Catwoman, he takes the battle to the Riddler's townhouse. The townhouse is severely damaged in the following chaos, but the Riddler is freed from Ivy's control in the process. Dismayed at seeing his house in shambles, he takes his old brass question mark cane off of the wall and begins to vent his frustration on the already downed Boneblaster.
In the present day, the Riddler digitally stole money out of Gotham's reserves when Batman ambushed him. Batman threatened to kill him, which surprised the Riddler until Batman revealed he was actually Katrina in the Caped Crusader's body. The Riddler was surprised by this revelation, and knocked out Katrina by electrocuting him/her. He then wraps her in chains above a tank of acid, where the Riddler asks, "When is Batman not Batman? And do you know what the answer is?" Katrina looks at him sternly, and Riddler answers "Who cares?" and comments on he would either be destroying Batman or Katrina in Batman's body, which he states is a win-win. However, Batman in Katrina's body, along with Nightwing, Batgirl, and Felix Faust, charge in and battle the Riddler and his henchmen, until Faust switches back Katrina and Batman's bodies. Batman then knocks out the Riddler again and sends him off to jail.
Batman steadily solved every riddle, with the Riddler boasting his superiority to begin with but slowly becoming more enraged with Batman. Before solving the last few riddles, Batman located the Riddler's signal and notified the police of his whereabouts. After solving his final riddle, the Riddler began to implement Gotham's "greatest riddle." But before he could do so, the GCPD broke into his hideout on 225 O'Neil Avenue in Old Gotham. The police arrive there and arrest Riddler as he quotes to Batman that he cheated on his riddles. Riddler question marks in Dr. Young's book are found on his page and many villains' pages. He saw the book and wanted to know about a professional's viewpoint on the inmates. Some might be easy to manipulate or great allies to have in his eyes.
The Riddler, challenging Batman with the greatest riddle of all ("Can Bruce Wayne and Batman ever truly co-exist?"), gives him the choice of rescuing either Chase or Robin. Batman distracts the Prince of Puzzlers with a riddle of his own; unable to resist, the Riddler takes his hand off of the control that would drop the two and listens eagerly. Batman gives his Riddle: "I see without seeing. To me, darkness is as clear as daylight. What am I?". The Riddler scoffs and gives him the answer: "You're as blind as a bat!". The Dark Knight affirms this answer, and activates the sonar-imaging lenses, allowing him to accurately hurl a at the brain-wave hub, shattering both it and the Riddler's massive intelligence. Before the Riddler collapses, he springs the trap doors in Robin's and Doctor Meridian's cages, sending them plummeting to their apparent doom. Fortunately, Batman rescues both of them before confronting Two-Face.