Passing through the gate, Aliya discovered that they were being scried by the marilith Drusii, whom they had recently confirmed was working directly for a powerful demoness called Lilith (lover and companion to Raguel). There was little they could do about that now, though.
Once inside the fortress, they encountered some massive, shadowy beings that spoke to them. They shadowy things revealed themselves to be the Soulriders and said they didn’t want to fight the Runewardens if they did not have to. The Soulriders seemed to know a lot about what the heroes had discovered and, in fact, had recently decided to help them rather than hinder them (or, they implied, to deal with the situation themselves). These creatures seemed as worried about the coming Night of Dissolution as the Runewardens themselves. The Soulriders gave the adventurers directions for getting through the castle most expediently and entering the Spire itself, where the Gates of Delirium created and maintained the Entropy Sphere. Not fully trusting them, the heroes used their own spells to divine the best way—although it seemed their mysterious benefactors were telling the truth.
The Soulriders warned the group of the Chamber of Burning Souls, and beyond it the Ageless Titan. The Chamber of Burning Souls was a hellish place of torment for victims of Ghul trapped hundreds of years ago. After dealing with its evil guardians, they encountered undead Cthorn, a race so evil it had been wiped out generations ago in the war against Ghul.
They persevered and made their way into a vast chamber of blackness. Crossing walkways of skulls that seemed suspended in an eternal, dark void, they fought against rhodintor: goat-headed demons that, like the kython, had been created by the Galchutt thousands of years ago. In the center of the chamber stood the Ageless Titan, a mummified undead being 30 feet tall. Rather than fight him, the group was able to parlay with the titan. They impressed him with the fact that they had been through the Seven Jewels of Parnaith, and Shurrin granted him a bag of holding filled with various magic items the group had gathered over the last few months that were too evil for them to use. The titan accepted the offering and caused the skull of an impossibly huge dragon to open and grant them access into the interior of the Spire and the chamber of the Entropy Sphere.
The Entropy Sphere was as bizarre as they had been told—a mass of congealed chaos brought into being at the confluence of six portals called the Gates of Delirium. And, just as they had heard, one of the portals was gone, destabilizing the sphere and causing the laws of physics and magic to alter without warning in areas around it called Pits of Insanity.
They were soon greeted by an Urthon Aedar named Baenarum, who was not at all surprised to see them. They did not even need to explain who they were. With his guidance, they entered the Entropy Sphere.