Riddler

An unnamed person, also known as the Riddler, is a criminal from Gotham City.

Biography
At some point in time the Riddler became a notorious criminal in Gotham City.

Catherine Hamilton mentioned the Riddler when forcefully reading Alice's speech She said that the real villains in Gotham weren't the criminals like the Riddler and the Joker, but people like her.

Behind the scenes

 * In the comics The Riddler is a super-villain enemy of Batman, named Edward Nigma, who commits crimes revolving around an obsession with riddles.
 * It is currently unknown if the Arkham Asylum patient E. Nigma is the Arrowverse version of the Riddler.