A One-Round Tournament
From the introduction:
Free Will stars six undead PCs, who begin the module under the control of an evil necromancer, Relgarth Blackblood of Addison-Conty Academy. Using his powerful negative plane prison, a black cube of force which can entrap undead, he has sucked each PC in turn into his prison. This necromancer has been away from the plane for several months, and in his absence, the PCs break free, temporarily, from their prison. Their quest involves retrieving the components of a ritual which will permanently free them.