"Play as the ruthless vigilante in the exclusive story pack," reads a promo image also advertising the previously confirmed Harley Quinn DLC, which is available at multiple retailers.
A PlayStation exclusive Arkham Knight Scarecrow Nightmare Pack has also been confirmed by Sony. "Tear through the city in the all-new batmobile and face off against a towering vision of Scarecrow and his undead army as they spread terror on the streets," reads a content description.
The PC, PS4 and Xbox One game was originally set to arrive later this year, but in June publisher Warner Bros. delayed the Batman Arkham Knight release date to 2015.
GameStop management recently said the company is working to extend its influence in the console publishing and development space in a bid to secure more exclusive content. However, the initiative won't result in the retail giant telling studios how to make content, according to CEO Paul Raines.
"I think we'd be foolish to tell developers how to develop games or publishers how to bring product to market," he said. "That's what they do extremely well. I think the day you see us in the creative side is when you can tell me we've officially lost our minds."