The first DLC for Assassin’s Creed Brotherhood will be released for free on December 14th.
The Animus Project Update 1.0 DLC will contain one a brand-new game mode and one brand new map for multiplayer. Here is a description of the new game mode:
Advanced Alliance will make the original Alliance Mode with target identification and engagement more difficult than in original Alliance Mode, thus providing a more challenging experience for players. With three teams of two players each, Advanced Alliance is a tougher test for players and rewards teams that use stealth techniques to hunt their targets.
And the new map description:
Located on a rocky tidal island of Normandy in France, the new map, Mont Saint-Michel, offers breathtaking scenery sure to enchant all. Its particular topography of narrow streets, high-perched bell tower and multi-leveled architecture is perfect for hunters and predators alike to surge from out of nowhere to execute their prey. To survive, recruits will need to use free-running and narrow roads to their advantage.
You can read more about Assassin’s Creed Brotherhood at http://www.assassinscreed.com/.