Here is a project I started some times ago and finally decided to work a bit on. For the fog, this time I used the usual trick, a sphere surrounding the scene with scattering medium material and a sphere around the camera to control the fog depth (where it starts to be more precise).
Modeled with Blender as usual
Rendered with Octane Standalone 4.0 RC5
Renderd time around 15 min, 25 min for larger images (3000x1680).
About fog :
As some of you aren't aware about the fog trick, here is a quick info :
Just create a volume to include the scene with normals pointing outside, create a sphere with normals pointing inside around the camera. The sphere should always be at the camera position. Set scattering medium material for both meshes and increase the size of the sphere to control where the fog should start. Play around with scattering settings to find the result matching your expectations ;) Hope this helps.