At first, I thought of this encounter that players could only find at night. It's a sudden cloak of mysterious fog.
...
WALL OF TEXT
Ever heard of text formatting? *eyes falling out*

I like the idea of fog. I dont have any cool mysterious encounter ideas, but fog as well as rain could make the existing maps varied and therefore more interesting too...
Imagine TC in foggy surrounding where you cant see a thing and sneaky one-hexers are about- new levels of adrenaline discharge for sure.
Also the lighting could use some darkening in the later hours.. I sometimes even can't tell if it's really night...
Yes please, more atmosphere.