“But hold your horses, young Edwin,” you sternly interject.
It sounds like a cheap, taboo-jabbing gimmick."
Friend, I once thought as you.

Not the nice kind of mysterious fog, mind you.
This fog is, basically, wee smoke.
And the world of Urge consists largely of wee.

Some of it erupts from the ground in stinking geysers.
The more fog there is, the more enemies there are, and the worse those enemies become.
Also, piss meteors.