Betrayal at Monadhan

The githyanki have been defeated, and the heroes' world is safe. Or so it would appear. But upon reporting back to the Coalition of nation states, the adventurers, now wielding power of epic proportions, learn of a new threat. Tiamat, using the githyanki as pawns in her endless struggle against her archrival Bahamut, has enlisted the aid of another ally -- a dark ritualist of immense power. Having lured this denizen of the Shadowfell to her cause ages ago, he has been working on something of immense power -- and great danger -- and only the heroes can discover how great this new threat truly is. They must travel through a domain of dread, and find a way to the ritualist's realm through its only portal...guarded by the domain's own dark lord.

Tiamat's black exarch, Mornujhar, has hidden away a ritualist of immense knowledge. The ritualist is in a dark realm, working on a ritual that will bring about Bahamut's doom. The only way to reach the exarch and the ritualist is to travel to Monadhan, the Domain of Betrayal, and pass through a portal there.