Arx Fatalis can be considered a spiritual successor to the excellent Ultima Underworld games. If you've never played or just want a way to go through it on another platform, thanks to the source code release and the Arx Libertatis project now hitting 1.0, you can now play it on Linux, Mac, FreeBSD, in addition to Windows. It should work on bunch of other stuff if you feel like tinkering, too.
For now it appears more or less a straight port of the original, but you can expect an editor and modern shaders to be added eventually.
You'll need a copy of the original game to get it going -- we'd recommend the GOG.com version if you don't have your own copy. Once you're set there, hit the source and enjoy this lovely RPG on your platform of choice.