I seem to remember a long time ago I used some light sources that made darknes.
What I'm after doing is making a cave entrance in the worldspace and I need (would like) to have it
getting darker as PC goes into the cave, at a given distance inot this cave there will be a trigger to
an internal cell. I don't remember the name of the light source and I'm also not sure if it was Oblivion
or Morrowind I used them, if you can't darken the main light source these made the area around them dark