- "When she was building it, Stasya considered Warrenhold to be an investment in humanity itself. She wanted this place to change the world."
Warrenhold is composed of eight towers, of which only the Entry Tower actually reached above the surface. The rest of the castle is entirely underground in a huge natural cavern. The towers are connected by bridges, although some of these appear to be damaged at present. Inside the Tower of Night is a pit that goes all the way down to the Undercrust. This pit was there long before Warrenhold was built, and was the reason why it was built where it was. Only six of the eight towers were ever named, since Warrenhold was never used in its intended capacity and those two towers were only ever used for storage.
The primary building material of Warrenhold was going to be a special Integrator-made stone called Nightrock. Nightrock had a number of interesting traits. Unfortunately, the process of creating nightrock was too time-consuming even for Stasya, and she ended up only building one tower and an inner sanctum in each other tower out of it. Nightrock has several interesting properties:
- Extreme durability: Nightrock is not indestructible, but it can stand up to a huge amount of damage before it will break. Voreese claimed that it would require someone of Harper's level or higher to damage it.
- Regeneration: even if it does get damaged, Nightrock will naturally repair itself over time. This was incredibly impressive, especially for the time. Even with more modern techniques, Haqq was extremely impressed with himself just for creating the regenerating material of Hector's Magic Shield, which was tiny compared to an entire castle.
- Aura of dread: Any living thing other than a servant will feel a vague sense of unease when near the stone of Warrenhold. This is weakest in humans who have had the effect explained to them and strongest in very unintelligent animals like instects. This was originally intended as a pest control measure, since Stasya had a particular dislike of insects.
The rest of the castle is also made out of special stone, but it only has a measure of Nightrock's unnatural durability and the feeling of dread, with no ability to self-repair.
The original purpose of Warrenhold was to serve as a trade center that would allow commerce between the surface world and the Undercrust. Unfortunately, This purpose was never realized and Stasya died without ever earning the respect she deserved both for her plans and her accomplishments. Hector never asked Voreese how Stasya died, because he assumed that the story would be very sad.
At several times in history Warrenhold was inhabited by kings and besieged by invading forces. Its defenses were only ever breached once, and that was only because the defenders allowed invading forces in so that the war could end. More recently, Hector was made Lord of Warrenhold and given the opportunity to restore and rebuild it. He made some progress before being called away to meet the Rainlords. How Hector's retainers fared after his departure is unknown.