Pretty much since the first announcement for Batman: Arkham Knight we have known that Harley Quinn will be a playable character for those that pre-order the game. Well it has also been officially revealed by Rocksteady that there will be a side story mode for the fan favorite femme fatale too. This story mode DLC will be in addition to the challenge maps that have already been announced.
Batman: Arkham Knight has been delayed until 2015. It will be available for PlayStation 4, Xbox One and PC when finally released. When you pre-order a copy today, you can get Harley Quinn as a playable character, plus other bonus content.