The city and catacombs of Saint-Denis will open up to Assassin's Creed Unity players on January 13th, Ubisoft have announced, and it'll be free for everyone as an apology present for releasing the game in such a poor state. Here's a thing I know about Saint-Denis: during the Revolution, the royal tombs in the Basilica were cracked open and their contents tossed into pits in the yard and oh no over the course of telling this story I realise this'll be the setup for Dead Kings. Of course it will. They have to Assassinate all of history don't they, those people. You can see a little of this fanciful retelling in a new cinematic trailer.
Continuing on after the story of Unity, Dead Kings will see Arno poking around Saint-Denis and having a good root around in its unexpectedly sprawling-and-filled-with-alien-technology catacombs. It'll bring new story bits, single-player and co-op missions, and weapons that'll carry over into the regular campaign too. Rattling off DLC feature lists is a little crass but hey, let's think of this like new missions coming in a patch. What a generous patch!
Here's another Saint-Denis fact coming at ya: the Basilica was supposedly founded upon the site where Saint Denis collapsed after walking and giving sermons for six miles. That might not sound impressive, but do bear in mind he'd just been decapitated atop Montmartre - you know, the hill with the steps at the end of Amélie.