Rocksteady announced a pre-order bonus DLC for Batman: Arkham Knight featuring Harley Quinn back in March, but something has changed. The new ads for the DLC appeared on GameStop are different. Not only they feature a different image of Harley, but the DLC itself has been renamed "Harley Quinn Story Pack."

While the description still mentions "play as Harley Quinn and receive 4 Exclusive Challenge Maps," the renaming of the package is peculiar, as seems to imply some sort of story content involved. 

At the moment Rocksteady did not offer any detail on the nature of said content (which could simply be a storyline involving the four missions mentioned, but the "end"  in the description may also mean that Quinn being playable and the maps are separate elements). We'll keep you posted as soon as more information is shared.

In the meanwhile you can check out the two promotional pictures (before and after the change) below.

Update: Amazon's blurb is clearer as it says: "Pre-order Batman: Arkham Knight to play as Harley Quinn. Utilize her unique weapons, gadgets, and abilities. Plus, contains 4 Exclusive Challenge Maps." It definitely indicates that the four challenge maps are in addition to Harley Quinn being playable, indicating that her content will most probably be story-driven.

Before

Batman_Harley

 After

BAK_bonusLG

[Thanks for the tip: Xenovia]