It's a young adult novel about a guy that is somehow dragged into a fight against the subterranians, together with a very quirky woman. We have a lot of stories about the little ones under ground (trolls, elves etc) in my culture, but here something really made them mad.
![Wink](https://i.mysupportforums.org/images/smilies/wink.gif)
They basically manifest by making ground into swampy quicksand type goo, earthquakes, sinkholes and other lovely things.