Those of you craving more Batman: Arkham City story content should already have marked your calendars for this bat-time and bat-channel. But just in case you forgot, the Harley Quinn DLC is available starting today. The DLC is already up on Xbox Live Marketplace, and it will hit PlayStation 3 and PC later today. It adds a new story mission for $9.99 (800 MSP).

As previously reported, "Harley Quinn's Revenge" is post-game content detailing the fallout of the big event that occurs at the end of the game. You'll play as both Batman and Robin as they delve back into Arkham City to uncover Harley's plans, which involve getting back at the Dark Knight for her perceived slight.

For those who bought the Game of the Year edition, you'll also get the various DLC packs of costumes and challenge rooms as well. It includes Catwoman, Robin, Nightwing, a slew of outfits, and seven Challenge Maps. The GOTY edition also includes a download code for Batman: Year One.