The Abyss of Thuvia
Fort Zalkine is the home of The Arcanaotheign, The Revered Queen of Pashow. Built largely with magic over the course of 100 years, it is the only truely safe place in all of Thuvia other than Merab. The worshipers of The Queen and her close family and allies live within the stone walls and passageways of the castle. It's protected from attack by the Flesh-Forged beasts of Nex that roam the mountains, and elite Oread warriors hand raised by her monks.
A day's journey from Pashow, most of her citizens have never seen the fort. Those that are invited are either captured by the Oread warriors and brought blindfolded to the castle, or lead in the dark by her Tengu scouts through the dark of night.