saveroomminibar:

Batman Arkham City: Harley Quinn’s Revenge. Trailer.

Below is an official FAQ for the new DLC:

HARLEY QUINN’S REVENGE

How much will it cost?
800 points on Xbox Live and $9.99 on Playstation Network

Do I need to buy the Game of the Year edition to play it?
No

Do I need to own Arkham City to play it?
Yes

When can I buy it on its own?
From May 29th onwards (both Xbox Live and Playstation Network)

Is it coming to PC?
Yes, we will be announcing more details soon

Are there new achievements?
Oh yes!

Who do I play as?
You will switch between Robin and Batman within the DLC.

Do I need the Robin DLC to play Harley Quinn’s Revenge?
No

How long is the content?
Over 2 hours and all new environments

Are there any Easter eggs?Is this the last DLC? What are you doing next?
You will have to wait and see!