Skyrim version can be downloaded here.
Dark Souls and Skyrim are all about atmosphere, and they both nail it -- in their own respective ways. But if you want to bring Skyrim's atmosphere closer to Dark Souls', you can do to Skyrim what every fantasy and sci-fi film director has done to their own works: add post-processing effects!
... or, have someone else do it for you!
The Grim and Somber ENBs are a collection of ENB post-processing presets meant to give Skyrim a darker mood. Don’t worry, it’s not as hard as it looks to install -- just follow the instructions and you’ll be good to go!
If none of the Grim and Somber ENB presets are to your taste (or you’re playing Skyrim Special Edition), just be aware that there are tons of ENB presets available at Nexus Mods -- you can find them all here (or here if you’re playing Skyrim Special Edition.)
Given the depth of Skyrim's modding scene, I'm sure there are plenty of mods that could fit on this list. Let me know of any that I may have missed!
If you're looking for more Skyrim-related content, you can find it all here!