It's like Sim City + Lord of the Rings + drunk dwarves. A fun game if you can stomache ASCII.
More info: It's a fantasy world simulator type game. When you first open it, it generates a world full of civilizations of different races, and then progresses their history a few thousand years. And then you can play Fortress Mode, which is sort of a RTS game where you dig and build and make stuff, while fending off attacks; or Adventure mode which is your standard roguelike adventurin' fare.
The background behind the game is pretty cool; it's being developed by the Adams brothers Tarn (or Toady, the programmer), and Zach (or ThreeToe, the writer). The game's in alpha right now, and the
dev plans outline a lot of the groovy features they're working on adding in. Currently they're hammering away at the army arc which'll have wars play out on the world map, and you'll be able to take part in them.
Overall, it's just cool that there's a game with ASCII graphics that requires a modern processor and a ton of RAM, simply because it's calculating temperatures and physics for all of the tiles.