All things considered, I did actually enjoy Assassin's Creed Unity a fair bit. It didn't build on any of the great ground work put down by Black Flag and it infamously had/has technical issues, but I did generally enjoy my time with the game.
That's why I'm interested in seeing what the Dead Kings DLC has to offer. Ubisoft have announced that the content will be out January 13th for PC and Xbox One and the day after on PlayStation 4. Best of all, it's free as an apology for the game's state on release.
Ubisoft outlined the story by saying:
After the events of Assassin's Creed Unity, Arno leaves Paris for Saint Denis, a mysterious city that holds the crypts of deceased French kings. Sent on a mission to the extensive underground of the Basilica, Arno will face a faction of new foes, the Raiders, populating its catacombs. Equipped with a lantern and a new powerful weapon, the Guillotine gun, Arno will have to navigate the dangerous passageways to uncover the darkest secrets of the city.
There is even this nifty trailer. It's got bad guys, catacombs, and eerie goings on. It's actually pretty cool.