There's a new Modding Guide on the Elemental War of Magic Website, as the mod tools are available as of beta 4 of the 4X turn-based strategy game. The article has details on file formats and an introduction to the mod tools. Word is: "During the beta process, the team will try as much as it can to help users learn what can and can’t be done with the existing modding tools. Those who need a lot of hand holding should probably wait until after release since the team will have very limited time available to document what is what until post-release."