Here's a (sort of) brief summary of what I've established about the Demon Verge setting, some of it extrapolated from Demonlord, and some of it made up whole cloth. This represents knowledge that player characters, who are not native to the region, would already know (or be able to glean with little effort).
The Kingdom of Altacia
Often referred to simply as "the Old Kingdom", Altacia is the largest human nation on the continent of Narth. It was once the preeminent power in the region, but is now in decline, challenged by its neighbors, the realm of Ekkesh (to the south) and the Demon Provinces (to the east). The Duchy of D'Ansor
A realm whose people have as much in common with the cragsmen of Altu'han as they do with the Altacian people, D'Ansor only recently bent the knee to the Old Kingdom. Its capital is home to the only magical college in the region. The villages of the Duchy are terrorized by brigands, deserters from both sides of the recent war.
The Principality of Timur
The largest city in the region, save Nisshar, Timur is the eastern trade hub of the Old Kingdom, now wracked by banditry. Once the stronghold of the Hosar faith, it was here that the High Priest was slain in battle, and Hosar's influence here is now as diminished as the spirits of those who were once its adherents.
The Barony of Barthek
A swampy land regarded as a cultural backwater in the Old Kingdom. Since the death of its Baron, Barthek is torn by internal strife between the Altacian nobles that have inherited it, and its people, whose traditions are closer to those of Ekkesh, a southern nation with a long history of conflict with the Old Kingdom.
The Kingdom of Ula
Until one year ago, the Dwarves of Ula toiled under the eye of the abomination known as the Balron and the Trolls that served it. Freed when the wizard Rabat slew the Balron, the Dwarves aided the alliance of Hosar in driving back the forces of Nisshar. Though freedom has come to the Dwarves, untold numbers of slaves yet toil in their mines, and it is said that slavers in Ula's employ still bring travelers to their mountains in chains.
The Duchy of Altu'han
The "mountain realm of the cragsmen", Altu'han is a northern domain ruled from a fortress city. Much of what is now the Duchy of D'Ansor was once the cragsmen's territory. Altu'han was briefly conquered by the Altacians, but its people have proven untamable, and for over a century the Duchy has been a part of the Old Kingdom in name only.
The Principality of Lyung
"Realm of the Sorcerer Cloud Prince", Lyung is an enigma even to its neighbors. What is known is that its capital is impregnable, and that none have been granted an audience with the Cloud Prince in generations. Legends say that the warriors of Lyung ride great dragons into battle, and indeed, some assert that they have seen the figures of men on winged creatures crossing the central plains.
The Great Woods
Home of wild warrior tribes, known worshippers of beast gods and forest spirits. Reputed to be not entirely human, the Great Woods barbarians are unpredictable, allying with Demons or men (or neither) according to their whims, and since the last war, the barbarians' raids against the eastern villages of Timur and Barthek have only grown bolder.
The Land of the Ancients
A nearly forgotten race, the Ancients ruled the hills and plains of the entire region in ages past, and their prehistoric ruins dot the landscape. It is said that the last remnants of the Ancients dwell in a crumbling temple to the north of Nisshar, and that the Demons give a wide berth to this land.
The Province of Nisshar
Westernmost province of the Demon Emperor's domain, Nisshar consists of several sprawling city-states and fortresses in a largely barren expanse of steppe, desert, and badlands. Each of these city-states is ruled by a Demonlord that swears fealty to the Imperial capital, Tor'zem, far to the east. The cities of Nisshar, Erush, and Taegul are places of despair, where men, demi-men, goblins, orcs and all manner of other beings live in common fear of the lash of their accursed masters.