Riddler

Edward Nygma operates under the guise of the Riddler as a private detective, although he was once a criminal.

History
Riddler was employed along with most of Gotham's other gimmicky criminals by Lex Luthor during his plan to take over Gotham City. Riddler actually acted as a mole in Luthor's ranks, leaking out information to Batman while making it appear as if Catwoman was responsible, an act which would later bring the wrath of the cat-lover upon. While Batman and his team were infiltrating Luthor's base, Riddler distracted him with a game of Battleship. Luthor soon came to the conclusion that it was really Riddler who had been giving Batman the information, but the Riddler managed to escape him.

Shortly after Luthor was dealt with by Captain Marvel, Riddler decided that Gotham City was maybe too tough for him and his fellow crminial "friends," so he decided to try another city---Metropolis. Riddler formed a group of seven (hence the name of the Magnificent Seven) other Gotham-based villains including himself, Killer Moth, Mr. Freeze, Jonah Hex, Catwoman, Scarecrow, and Gathit. Upon arriving in Metropolis, the group decided to take out the local hero, Superman, who they figured was not nearly as good as Batman. Riddler devised a plan wherein Catwoman would pose as a damsel in distress being attacked by one of the others, and then while Superman was distracted the rest of the villains would use their various attacks on him. Much to their surprise, Superman was able to easily shrug off all of their efforts and arrest them all.

Not too long after this event, the Riddler decided to turn over a new leaf and use his skills on the side of justice rather than continue to be a criminal. He has worked alongside Batman, Nightwing, and Robin (who he often argues with about the debatable stupidity of his Riddles) with numerous cases and mysteries. The group has become so trusting of Riddler that they bring him into the Batcave regularly, and he even knows that it is located beneath Wayne Manor; although he believes this is just a farce Batman uses to make anyone who knows its location think he's the millionaire playboy Bruce Wayne.

Riddler has shown an unexpected amount of skill in hand-to-hand combat; however, his primary flaw is that he can't take a punch.

Riddler was hired by District Attorney Adrian Chase to investigate the criminal workings of the Black Mask and his organization. When Chase became the bloodthirsty Vigilante, he broke into Nygma's office holding a shotgun. It seemed as if he was going to kill Nigyma, blaming him along with a long list of other people for the tragedies that had happened to him; however, he spared the Riddler's life in return for all the information he had gathered on Black Mask.