I'm playing on elvishly easy with permadeath. At least since the 3th or 4th floor, almost every time I encounter an enemy I get debuffed with the Shroud of Darkness.
I'm at level 7 now and the situation hasn't changed.
It is really unpleasant, since the effects stack and most of the time I can't see a single tile around me.
How can I get rid of it? Is there a way to find out what/who cast it at me? [I am playing with a handful of mods activated, but I've once beaten the game with them and never had this problem, so I don't suspect the problem lies there.]