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.
A fallen clock tower holds components from an ancient artifact. Upon discovery of the components, competing agents look to launch expeditions to uncover additional components scattered across distant places—and times. The now-lost Temple of Moloch and the construction site of the legendary Tomb of Horrors are two of those locations. However great the risks, finding the components demands the effort, for whoever does so can reassemble the fabled Infernal Machine of Lum the Mad!