The reason this is not craftable was by design. I am going to make a large quest chain for this mod which will grant you the ability to choose 1 of 10 rings which each grants a different aura effect. This will take me a large amount of time so I am simply going to be building on this mod slowly.
To see the effect this ring produces, watch this video:
To get this ring in game just type in console:
player.additem 0020000c 1
To choose a different smoke effect I have paired this mod with my other mod which allows you to choose a smoke effect(which eventually will all be one mod, but for now it is separate). The files for that are a separate download that you can get here:
Installation: The Ring: just drop the RoS.esp and textures folder within the ring of shadows zip into your skyrim Data folder, make sure to load it from the launcher.
Here is another mod of mine that removes the smoke tendrils but leaves the base color, use it in conjunction with this if you want the base color change but not the smoke, it is located here: