From the update:
The dark and foreboding caverns of an entire subterranean world, home to dark elves, deep gnomes and worse, plays a large part of the overall story in Seventh Crown. The races of both worlds mix and mingle much more often than in other fantasy settings, allowing for dark elven characters to fit in seamlessly with surface groups and adventures down in the depths to be as normal dungeon crawls.
In Seventh Crown, this "world under the world" is called The Great Beneath, and today we have a fantastic update in two parts. First we have the graphic release of the map showing the Great Beneath from the amazing cartography skills of Tim Toolen. Not only does it show some landmarks such as the unfathomable Hellsfont crevasse and fields of fungus forests, but it is a perfect overlay of the surface map of Kanis to show where the two worlds co-exist and create two sides of the same coin.