Scions of a Scholar
The Grand Conjunction was the culmination of a decades long scheme by Azalin Rex to create a dimensional rift so that he could escape the dread realms. Held together by the Hexad of Hyskosa, a prophecy by the vistani dukkar Hyskosa, this series of events unbalanced the coherence of the realms to the point that the dread lords would be forcibly expelled.
The conjunction expelled them all to a unspoiled world in the Prime Material plane. The heroes were able to unmake the conjunction by sending the cursed lords back into the dread realms.