Roduka

Exiting the ravine maze, the party found itself on a large, boulder ridden, plain. Off to one side, they noted an encampment and upon further investigation, found it occupied by Shadar Kai, led by none other than Roduka.

She gave them the following information:
1. There is a teleportation circle in the base of the Tower. For years it, and the tunnels around it, had been rarely used or occupied. Now it is a hive of activity as new undead are created there on a daily basis. There is a teleportation circle that will allow access outside of the Shadowfell.
2. Undead pour out of the Tower at an unprecedented rate. This is why the Shadar kai cannot advance against the darkness in the Shadowfell.
3. Recently, Acererak’s followers have begun trying to animate a purple worm to place under his control. If the party finds the chamber this is happening in, please destroy it and anything in it…if this creature comes into existence, the Shadar-Kai would be unable to defeat it.
4. Finally, she tells them the story of Acererak

Acererak the Devourer was born a cambion, the product of a balor named Tarnhem who took his human mother by force. Apparently an ancient conjurer summoned a demon that was far beyond his ability to control. The demon devoured the wizard, and forcibly conceived a cambion son in one of the wizard's servant girls.

Acererak's mother survived her son's birth, but she was killed by a torch-wielding mob ten years later. The boy was rescued by none other than Vecna, the Whispered One, who killed the advisors that urged him to kill the child and instead took the half-demon on as an apprentice. Even then, ten year-old Acererak loathed life, looking forward to becoming undead like his master. During Vecna's siege of Fleeth, the lich was severely wounded and rescued by Acererak. Vecna subsequently promoted the cambion.

It is unknown if Acererak was present when Vecna was betrayed by Kas the Bloody-Handed, but at some point, he moved to the Vast Swamp where he constructed a lair for himself, colloquially known as the Tomb of Horrors. While alive, Acererak built a subterranean temple complex in the name of Orcus, burying its architect and all of its workers within. Eventually, Acererak succumbed to the lure of lichcraft, and had himself buried in a labyrinthine tomb where he committed himself to his studies and, eventually, demilichdom, abandoning his body for the planes beyond.

During his last attempt to seize power in Idera, he built this Tower as a base of operations, giving each of his Lieutenants their own spire to use as a lair and lab. Morbius, Simon, and Keraptis you are familiar with. Very little is known of the last one.