The Dark Peak Bestiary
The murk is the persistent fog and cold dampness that constantly covers Hellsborough and The Dark Peak; blocking out most sun and moonlight. Organic in a large part, due to the general foulness of the weather in the area, it is supplemented by the nascenti constructed humidity plants dotted across The Dark Peak, and exists for their benefit, but also all of the all of The Dark Peak's denizen races including the xin, exacid, clown, dyapnid, mentiloth and cryptobite, who all benefit from the additional moisture in the air.
The murk is thick and dense, an oily, clinging, odourless effluent that sticks to clothing and at best provides visibility no better than ten paces ahead. As such, it maintains a fear, whether or not it is warranted; legend and myth has it that the murk contains "ghosts" -- there are (at least) two types -- syncarid -- variably sized stingray type creatures capable of enveloping and stinging anyone to death, and morivarid piranha type fish that suck the eyeballs and tongues from anyone who comes across a shoal of them as they swim through the murky ether. The murk also protects various other cryptids from greater exposure, including the don bog beast and barghests.
The murk makes breathing more difficult for humans, hence the use of psycmasks for breathing in the valley at Hellsborough (psycmasks also provide Augmented Reality, which is necessary due to the poor visibility, as well as nutrition), but only extends rarely into the higher lands of the Nether Land on the other side of the great railtrack, at places like Southey and Pitsmoor.