An expansion on the original Tomb of Horrors with plot and explanation. Contains a facsimile of the original adventure. The Dark Intrusion is causing the dead to rise from their graves. This is linked to a being known as the Devourer. Following the trail of Desatysso, a wizard who followed a similar quest, the players must enter the Tomb, and beyond that, the cursed City that Waits and the Fortress of Conclusion.

In the aftermath of AD&D Second Edition's "Return to the Tomb of Horrors," the demilich Acererak was thought destroyed. In truth, his spirit lingered and now after eons he schemes once more to achieve divinity. The characters must travel to three extraplanar dungeons, in addition to the remains of the original Tomb, in order to stop this from coming to pass.