Black Raven Dragoons

The infinite dungeon. At least, that's the way I've seen it described in one place. Fractals of the Mists will be introduced in the lost shores content and it sounds like an interesting challenge that scales difficulty up as you play. I look forward to spending some time adventuring in it. Not a bad idea on Arenanet's part. Here's an article with some gathered info on the dungeon and what to expect.