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Featuring over two hours of fresh gameplay, it'll be available to download beginning on May 30 on PS3 and Xbox 360.

Warner says: "The Harley Quinn's Revenge mission sends players back into Arkham City to face their final challenge as they interchange between playing as both Batman and Robin.

"Gamers must utilise each of the characters' unique combat and investigative skills to uncover Harley's vengeful plan and shut the gates on the urban mega-prison forever. In addition to experiencing a new storyline, fans can explore new environments and face-off against Harley's all new gang of thugs."