While I was looking for Arx Fatalis mods and modding tools and stuff, I came across this other game based on Arx Fatalis universe, Arx Catayst. This one is being developed in the Unity3D Engine. It's about Kultar, the guy next to you in the goblin prison. The game will take place before the events of Arx Fatalis and probably will take the gameplay on the surface since Kultar is part of the Guild of Travelers.

Here's the link in parts since I'm not allowed to post links:
http : // arxcatalyst . weebly . com / index . html