The Riddler is a clue-dropping criminal who delights in challenging Batman and Robin with his riddles that he leaves behind at crime scenes, always pointing to where he will be next. Although he was a high school dropout, Riddler is still intelligent enough to give the Caped Crusaders plenty of headaches solving his clues, which are often many-layered and contain several possible solutions. He is a member of the United Underworld and considered to be an arch-criminal on par with the Joker, Penguin and Catwoman.