Arden is all forests, and within its bounds can be found many worlds. One of them is a dark place, whose skies are marked by clouds and lighting, visible in slivers between the long fingers of the trees. This place is Weirmonken, and it is a fearsome place. What civilization there is has been carved by main force out of the body of the forest, small clearings connected by tenuous roads, threatened on all sides by the darkness between the trees. It’s a daily fight, and the forest always wins in the end, but new clearings get carved, new roads laid down, and each generation endures. They huddle around the fires, bolt their doors, say their prayers and tell stories of a glorious past, when they ruled this land from great castles, long since swallowed by the woods. These stories seem like so many legends, but every now and again, a woodcutter finds something as he clears the brush. Ruins, walls, statues - things with no clear origin.
This is Weirmonken to the visitors, and to the people who huddle in the night, but they are not alone. The woods are alive with predator and prey. The trees keep silent vigil over beasts of every stripe, some in numbers, some unique creatures that have hunted longer than an oak’s memory. To these beings, the spots of light on the map are little more than distractions - specks on the face of the endless forest.
Between these two worlds walk the Weir. Belonging to neither, the woods are divided among a handful of clans who squabble, fight, cooperate and hunt between and among themselves. To an outsider, the differences between one clan and another are hard to spot, but among the weir, they are everything. Matters of loyalty, fidelity, and the relationship with the people of Weirmonken are decided by the clan.
The clans are more diverse now than they have been in the past. It is said that when the Weir first hunted Amber, they did so under one great warleader, serving at his command and following the paths he sent them on. They failed in this great hunt, but the warleader also knew how to hide, and Amber cold not find them when they went to ground. The death of the warleader in the hunt left the Weir fragmented, and they were content to hunt the woods for many generations.
Until the moon spoke. The dancer came, promising hunts out of legend, hunts to guarantee the ancestors joy in heaven, and he lead them against Amber once more, with promises of a path to heaven from the top of the sacred mountain. He was not as great a leader as the Great One, and he was slain by Prince Eric of Amber, who hunted the people back to the Forest with fire and silver. He claimed a castle, long lost to the forest, as his own and from it his hunts road out like terror itself. This was a dark time, and the weir’s fate was in great danger, and it was only when an Elder braved the guards and found his way to Eric’s chambers that the matter resolved.
It is said that he caught Eric by surprise, and could perhaps have slain him there, but he knew that many had underestimated the fangs on this one, and he had another plan. Instead of fangs, he showed belly, and bent knee to this regent. Not every clan went along, choosing instead to retreat into the depths of the forest, but most chose this path.
Since then, there has been some small trade between Amber and Weirmonken, but not much. The forest is tamer, but that is relative - it is still an unfriendly place, and has little to offer to Amber save terror. Terror, and loyal soldiers, who are another kind of terror themselves.
To the villagers of Weirmonken, life is simple and horrible. They carve out what safety they can, try to get by, but the forest always threatens. Save for those few who have found their way to the regent's protection (for he does not seek them), life is fraught with peril. Some villages have found unique ways to protect themselves, but those are generally stalls at best. Those villages that thrive tend to do so with help (witting or otherwise) from the true masters of the forest: the Weir.
The weir are the largest group in Weirmonken, though the vastness of the forest is enough to emphasize the gap between "largest" and "dominant". Each clan is a complex network of blood, violence, tradition and necessity, and each has its own rules and behaviors. Some prey on the villagers, some quietly protect them, some actively mingle with them (though such villages gain dark reputations as a result). Similarly, their internal rules are very individual. There are rough traditions of respect and communication between Clans, but peace often results from the simple, practical problem that Weir have killing one another.
In the past, the Weir were frequently pawns of the gods, spirits and devils of Weirmonken. Gods have set themselves up as clan leaders and directed the weir as suited their own ends at numerous times in the past. Some say this is a result of the Weir tendency to superstitions, but others hint at a darker explanation. Whatever the cause, the disaster the Dancer brought upon the people smashed this principal, and Eric's strong leadership buried it. This is not to say that religious practices do not still exist among some of the clans, especially those who fled the Regent's rule, but most weir have learned the potent lesson that a god is just a dangerous form of prey.
To the villagers, the geography is greatly restricted - clearings and paths forming a fragile network of civilization. For a village, there is no greater fear than losing their path. Without it, they must accept the inevitable closing in of the forest, or strike out blindly into the woods, something that rarely ends well.
For the Weir, the geography is far more dynamic. Excepting a few fixed points, like the Regent's seat at Silver Spire, it is a shifting array of territories and hunting grounds, constantly marked and updated as clans travel or new prey and predators migrate. Places matter less than who and what can be found in them.
Weirmonken is a strange place. It's borders are ill defined, literally and metaphorically, and things tend to slip into and out of it to and from shadow. When the Weir previously marched on Amber, they slipped through these cracks, and Eric's shadowpath widened one of them.
It's hard to say whether it's cause or effect, but Weirmonken is full of magical creatures, mostly unpleasant ones, and many of the monsters who find their way into Arden do so from Weirmonken. What no one knows is whether this concentration of power causes the loose borders, or if the borders have resulted in this creatures finding their way into Weirmonken. Unfortunately, the lack of real history past a certain point has left the origins of the shadow and its ruins entirely in the dark.