Shadows feature prominently in this campaign, from the shadow monsters to D'alton's silent, lurking, gunslinging shadow. Ok...so that is just two things. The whole point of these blog articles or whatever you want to call them is to explain what would have happened in the campaign. I still have secrets about the world, like I haven't explained Gorelon or the Nel or Keroen Skathos or anything like that, but I have explained A'lst and the clones and whatnot. Anyway, shadows.
So we have these big black semi-transparent semi-two dimensional twelve foot tall shadow things that exude this awful numbing chill and drain energy from stuff. They are the Vacusu, they are the fifth Elder Race, the youngest, and their sole purpose in existing is to devour everything. At one point they lingered at the far distant reaches of the universe, and to a certain extent they still do, they kind of keep it from extending beyond its ability to sustain itself and eat the distant remnants for sustenance.
The biology and reproduction of the Elder Races is kind of bananas. I wish I could explain, but that reveals secrets. The Vacusu devour life and energy and their life cycle is tied to that devouring. Long story short, Vacusu reproduce by hollowing out planets and laying eggs in the molten core of the planet, the eggs absorb the energy of the core and hatch, eventually, it takes a while. When they hatch, the planet kind of cracks in two and turns to space dust as the eggs have finally completely consumed the core of the planet, which is never a good thing.
As the eggs absorb energy and life, they tend to hollow the planet out and cause the lines of reality to blur and the deep interior of the planet kind of becomes a very cold and weird place. One of the reasons the underground areas of The Known World are so chilly is because the core of the planet has nearly been consumed by the Vacusu and their eggs. Luckily enough, a Conteog (A'lst), a Saevoi, a Lacerat, and an Everseon have decided that they like Hekinoe (for a very specific mysterious reason that would likely never ever get explained) and have misplaced the eggs across the planet in an attempt to forestall the final stages of this hatching process. The shadow monsters, in between bouts of hunger where they decide to slurp at Nakmander's artifact, are hunting for these eggs, which is part of why they have become so visible in the past five or so years.
So there is this door in Derf's old room in the Braun family mansion. A very very cold door that the guys were very hesitant to investigate when they first woke up. I assume they have forgotten completely about it at this point. This door was created by Derf as a means of quick travel to The New Empire, it leads through a very dark place that eats life. When D'alton shadow jumps around, he flits in and out through the warmer shallower sections of this place. This place is the bizarre void created by the devouring nature of the Vacusu eggs. The void still exists within Hekinoe, Hell, if you dig deep enough into Hekinoe you will literally fall into the void. But that is deep deep, like deeper than the dark places where the Dwenoren first began gnawing on rocks to build their empire.
This empty void is so cold and alien to the minds of mortal creatures that they cannot truly process it. I imagine Derf found it cozy when he wandered through it though. So, the human(oid) mind being what it is, they fill in the details. The place ends up full of winding passages and staircases and massive monoliths and dark and winding architecture and it is never the same to any two people, or even to the same person. You can't map it or store things there, the whole place exists beyond the comforting normalcy of reality. Time and space are relative terms, so D'alton may spend a week in there to cross sixty feet with his shadow jumping, but he blinks right in and out when he does so in the real world.
Fundamentally, this boils down to this place being the Plane of Shadow of my universe. Any questions?