"SO CONFIDENT IS HE IN HIS GENIUS THAT HE LEAVES BEHIND CLUES AND PUZZLES RELATED TO HIS CRIMES..."
PIC(S) INFO: Spotlight on preliminary sketch art of Batman antagonist and member of the Legion of Doom, the Riddler, artwork by Alex Ross for the "Justice" (2005-'07) maxi-series published by DC Comics.
ORIGIN: "It is easy to think of the Riddler as a creature of pure pride. So confident is he in his genius that he leaves behind clues and puzzles related to his crimes and dares the police to try to solve them. Yet is there more to it than that? When you consider Edward Nigma, I am forced to face the possibility that the greatest tragedy of his childhood was the presence, not absence, of his father. There is a story about Edward being caught cheating as a boy.
I cannot be certain, but upon piecing the little information still available, I have the suspicion that Nigma's father punished him severely and maliciously for this and insisted on one thing -- that from that moment forward, his son would always speak the truth.
So if Edward was forced, verbally and physically, during an age of natural preadolescent rebellion, to speak the whole truth regardless of consequence or prudence, what then?
It wasn't until his father died that Edward turned to crime. But his crimes were unique. He left riddles that, if understood, would be an admittance of guilt. Could these clues be part of a compulsion to speak the truth? Is it in response to guilt? Perhaps it is the result of a cruel father's zeal to raise an honest son. This could be the tragedy of the Riddler."
-- BATMAN, from Bruce Wayne's Private Files in the Batcomputer (script by Jim Krueger)
Sources: https://www.zipcomic.com/justice-2005-issue-2 and www.comicconnect.com/item/886358.