Along Nidal’s eastern border, in the foothills of the Menador Mountains, the small fortress city of Ridwan serves as the center of worship for the faithful of Zon Kuthon. The walled military city of Ridwan is ill suited, in many ways, to support life, surrounded as it is by blasted volcanic fields of blackish, crumbling powder and jutting rock-falls — only the power of the divine can bring forth food or water to this terrible place. It was here that the people of Nidal beheld the emergence of their savior, the Midnight Lord. And it was here that the blessed of that faceless god nourish more than 10,000 devoted souls. In the wastes, the mighty soldiers of Zon-Kuthon train on shattered soil to defend his lands and to extend with guile and steel his power into the rest of the world.
Adherents believe that the twisting rift limned with black flame and cloying smoke in the city’s central square is the spot where the Midnight Lord first emerged upon Golarion. The site is a powerful gate to the Deeping Darkness, a particularly vile chasm at the heart of the Plane of Shadow, from which Zon-Kuthon’s clerics pluck legendary nightmare beasts. Once sufficiently dominated and broken to the will of the Umbral Lords, the otherworldly shadow-spirits serve Nidal at home and abroad. Since the fall of Nidal 370 years ago in the Everwar, “abroad” has most often meant Cheliax.
Sources: Pathfinder Chronicles Campaign Setting