The Hidden Secrets DLC will add some new things to your Assassins Creed 3 experience, but you must be a season pass kinda guy. In the Hidden Secrets you will get three new missions: Lost Mayan Ruins, the Ghost of War, and a Dangerous Secret. They are not huge sprawling mission though, and will take about an hour to complete. At least you will unlock two new costumes called the Aquila's uniform and a traditional colonial assassin outfit. There will also be more multiplayer characters for you to use for online Assassinating. If you do not have the season pass you will be able to buy Hidden Secrets on December 13th.