Eh, no offense but this suggestion is kinda, 'useless' and alot of people might get mad from the forced fog, but I guess you could use it in RP, it would be annoying but yea it could work.
Why not go ahead and suggest weather instead? Day and night cycle with random bouts of rain, fog in the mornings, snow in the cold seasons, etc.? All toggle-able, of course.
Except, you know, that it's already been suggested.
Very rare weather effect that gives a light level JUST dark enough for mobs to spawn (in the fog) so it is like where you walk it lights up so you're walking and BOOM creeper.
Except, you know, that it's already been suggested.
Relic of a bygone age.
The statement above is false.
Very rare though, like .7%