Edward Nygma (New Earth-Six)

The End of Heroes
When all the heroes began to die, Riddler went into hiding to come up with a plan to deal with the all the other villains who will try to take over Gotham when the remaining heroes die.

The Civil War of Evil
When the war between the The Secret Society of Super-Villains and the Injustice League began, Riddler remain in hiding due to a distrust of both Lex Luthor and Ra's al Ghul. Riddler eventually came out of hiding when he was contacted by the leader of a new faction of villains known as the Legion of Doom. The leader of the Legion offered Nygma a position in the Legion and offered him the use of the Legion's base in slaughter swamp and gives him the coordinates for it. Riddler proceeds to tells Legion Leader he will think about, which ends the conversation between the two.

Riddler would consider the proposal and eventually travel to Legion's base in Slaughter Swamp after his safe-house is attacked by Checkmate who believed it to be a Society safe-house. Upon arriving the Legion's Leader contact Riddler again and asks if he has accepted the position, which Nygma response with a yes.