The Riddler (Edward Nigma) is a fictional supervillain appearing in American comic books published by DC Comics, commonly as an adversary of the superhero Batman. The character made his first appearance in Detective Comics #140 (October, 1948) and was created by Bill Finger and Dick Sprang. Depicted as a Gotham City criminal mastermind, the Riddler takes delight in incorporating riddles and puzzles into his plots, and leaves them as clues for the authorities and Batman to solve. The character is one of Batman's most enduring enemies and belongs to the collective of adversaries that make up Batman's rogues gallery.

In the 12-part storyline "Hush", it is revealed that Riddler suffers from cancer, which also afflicted the mother of Dr. Thomas Elliot. Riddler uses one of Ra's al Ghul's Lazarus Pits to rid himself of the disease, and offers Elliot the chance to cure his mother as well, provided he pays a large sum of money. However, Elliott is in fact eager for his mother to die in order to inherit her fortune. Elliott, who goes on to secretly become the masked criminal Hush, explains he wants to get revenge on his childhood friend Bruce Wayne. The two of them agree to work together and Riddler sets Killer Croc, Poison Ivy, Harley Quinn, Joker, Clayface and Scarecrow out to destroy Batman, with Ra's and Talia al Ghul and Lady Shiva being temporarily drawn into the scheme as well. During the psychotic break that follows exposure to the Lazarus Pit, the Riddler deduces Batman's secret identity and that the late Jason Todd was once Robin; he then reveals his knowledge to Hush. He has Clayface shapeshift into the form of Todd in order to torment Batman haunted by the former Robin's death. Batman first thinks that Riddler had stolen Todd's corpse and hid it outside of Gotham Cemetery, but it was revealed in a later storyline, Batman: Under the Hood, that Todd was alive the whole time and had personally played a role in Riddler and Hush's scheme. When the Riddler threatens to expose Batman's secret identity, the Caped Crusader mockingly labels it an empty threat, pointing out that if Riddler revealed the answer to the riddle "who is Batman?", it would become worthless, something Riddler would not be able to stand. In addition, Batman warns him that if he reveals the secret, it would give Ra's al Ghul a vital clue that he used a Lazarus Pit without his permission, and the League of Assassins would subsequently retaliate against him.Answer this question using a quote from the following article:

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When the Riddler threatens to expose Batman's secret identity, the Caped Crusader mockingly labels it an empty threat,