The group travelled through the mirror to Faerun, where the Underdark was being overrun by Undead created by Briarus’ staff. They eventually managed to navigate the tunnels to Menzoberranzan, where Aeyliss and Yurt were defending Arach-Tinilith from the endless hordes of the dead.
Despite their stealth – and a number of Cunning Plans – used to reach Menzoberanzan swiftly and silently, the group decided to pick a fight with the vast army besieging the Drow fortress. It quickly became clear that while they vastly outmatched any of the entities that made up the shambling horde, the numbers would eventually overwhelm them. Especially as more and more undead Beholders were rising up out of the ranks. Adopting the better part of valour, they ran for the fortress, and managed to avoid being slaughtered.
Here Aeyliss told them that the undead had been dealable with, but recently had begun adopting strategy – she felt they were beign controlled, and while little could be done to lay the entire horde to rest, perhaps killing this controller would allow some fragment of a chance.
The group used Aeyliss’ long neglected House Insignia to teleport to Ched Nased, another (long abandoned) Drow city, and descended far, far beneath it. Here, they found an ancient tomb city. Carefully negotiating its trapped entrances, they encountered a robed figure – a lich, they thought – in conversation with a Lord of the Tower. Attacking it, they discovered that it was not, in fact, a Lich – but something far worse. It was three Demi-Liches acting in concert.
Despite being outmatched, the group managed to triumph (mostly by tricking the Lich into detonating several high level spells on its own position). At this point, they looked around, and saw tens of others shambling around the pillars flanking them. As they readied their weapons for a futile death, the leader the Demi Lich conclave stepped forward, and offered them a chance. They were no more happy with their dead comrade interacting with the outside world than the living were, and so in recompense, they would allow the group to leave – as long as the group was willing to have their memories of the Lich Conclave wiped.
This was accepted, and the group found themselves teleported to the ruins of Waterdeep, and from there, swiftly returned to Dreamkeep.