Batman: Arkham City - Harley Quinn's Revenge

Summary pulled directly from Steam - Some text may only be applicable to Steam platform

As the dust settles in Gotham, Batman is lured back into Arkham City by its last remaining super-criminal; Harley Quinn. Now more dangerous than ever and leading a homicidal gang of her own, she is hell-bent on taking her revenge against the Dark Knight.

Batman: Arkham City 'Harley Quinn's Revenge' DLC sends players back into the urban mega-prison to face down it's final challenge. Playing as both Batman and Robin, gamers will utilize each of the heroes’ unique combat and detective skills to uncover Harley's vengeful plan and close the book on Arkham City forever.

Key Features:

Play as both Batman and Robin as the high-stakes story unfolds
Face off against all new Gang’ enemy types
Traverse the new environment using Robin’s unique navigational abilities
Collect 10 Achievements
Over 2 hours of unique content