It was hinted before, but now it's official: this is Dragonborn, the first piece of DLC for Bethesda's open-world RPG Skyrim.
Looks like there are some trippy new areas, although I can't tell if any of them are from Morrowind, as a previous patch had suggested. Sure looks like they are!
Dragonborn is out on December 4 for 1600 Microsoft Points on Xbox Live. No word on a PC release yet, and none of Skyrim's DLC has made it to PS3 thus far, so if you've got the game on PlayStation... well... sorry.