The group decide to check the cellar of the tower first. In the basement they happen on a scene of cultists surrounding a summoning circle which according to Nimue is of superior craftsmanship. As above, the scene is frozen in time. On the other side of the room is a familiar gate to the abyss which resembles the one below Shadowdale.
Unaffected by the magic of the tower there's a demon at a blood basin similar to the one below the inn. He turns into a familiar figure, one of the head assassins in Shadowdale. He confirms that the cultists seem to be working for the Devourer and thus are beneath notice. He however is serving a greater master, Bhaal. Also he's been tasked to procure the black book from Sister Tara. Apparently his group has been trying to create a new such book in Shadowdale before the adventurers put a stop to it and helped seal the portal.
The Mentor finally rejoins the party downstairs and they decide to put a stop to the demonic rogue. The Mentor suggests using the circle to open a gate to the Astral Sea and request help from Mount Celestia…which might be necessary as the assassin immediately leaps into action stabbing Nimue and downing her…or not, since she's semi-undead anyway and thus is not stopped as easily.
Shiel punches s cultist at the circle in the face to drive him from the circle which also reanimates the remaining cultists. The assassin is shocked that "Bhaal's dagger" didn't put an end to Nimue. A chaotic melee erupts. The cultists are luckily pretty aimless, even the assassin has problems picking his marks.
Two hound archons burst from the circle and also assault the assassin. Hit from all sides he transforms back into a demon and leaps into the blood fountain, not without threatening dire consquences to the party.
The Mentor explains that the ritual to summon the hounds has been a part of the magic practiced by the paladins of the Order of the Sword. The archons ask Thana how the "capture of the traitor, the Rakshasa is coming along?" Thana replies that her current reincarnation doesn't have her full memories back. The archons tell her that "the tower can help her with that".
One of the archons sacrifices his essence to close the blood well, one of the altars dedicated to Bhaal.
The remaining hound archon reveals another scene from the past, apparently on the Astral Plane. Shiel as Shraevyn receives some Elven knights of Myth Dranor and Odos who brought him the Githyanki blade in exchange for a mind flayers head. But apparently "Shraevyn" is really a deva. Loathing Elves and not wanting any witnesses to the origin of his soon mighty sword, he slays the knights. Thana is horrified and steps into the scene to stop the Deva. She turns into a former, mightier incarnation of herself. Shiel, who partly relived the scene, reappears on the floor with gaping hole in the chest. Apparently he's dead. Does this mean Shraevyn never returned from his quest into the Astral Sea but was replaced by an evil Deva?
The Deva, Cersos, accuses Thana of being inactive in the great Elven war called "The Crown War", in which the Dark Elves turned into drows. Cersos on the other hand had aided some of the elfs, but was later betrayed by them. The slipping Deva was incarcerated on the Astral Plane. The only way to rectify things is to take the mantle of rulership for himself!
Thana cannot let this happen so she casts him down to live as a rakshasa until he atones for his sins! Cersos is beside himself with rage and uses this moment to call on Pazuzu who appears in the summoning circle! Apparently Cersos is ready to convert to Pazuzu! Thana steps between them and fights Pazuzu. Cersos grabs the sword and flees. While Thana turns to him, Pazuzu strikes her down! The vision ends and Thana returns to her younger self. She is deeply irritated by what she has learned. Memories of lifetimes spent in pursuit and combat flicker before her inner eye. Chaunteas mission to strengthen the faith may be the mission of her current incarnation, but the hunt for Cersos has been her mission for centuries and millenia. And something personal still seems to be missing from her memories. Something deeply painful. Something that is connected to the fairie puppet.
The Mentor and the remaining hound archon reseal the gate to the abyss. Shiel luckily isn't dead, but the final fate of Shraevyn seems to have been revealed!
According to the servitor golem the Zhentarim seem to have breached the 2nd and 4th floor. They're in the eternal battle however.
On the 3rd floor Shiel, this time as Shraevyn/Cersos faces Gothyl/Hedistrin once again. Apparently Cersos used part of Hedistrin's soul to be able to tap on her psionic powers and control it. Cersos charges Gothyl to impale her with his sword but the claw of Pazuzu around her neck bursts into flames and incinerates him. This has been the end of "Shraevyn" and one of Cersos' previous incarnations.
At least Pazuzu must have had a lot of fun pitting his own pawns against each other.