One of the past years greatest mapsets has been definitely Brotherhood of the Ruin (original download) by Kristian Aro. Many of us have been desperately waiting for a sequel to this - and damn, today is your lucky today - The Lost Temple has just been announced. It's currently under heavy development and it will definitely take some time until it's released but you can follow Kris' progress in the official Doomworld thread, take a look at some screenshots and also get an idea what you can expect.