The Tower of the Bone Devil

From publisher blurb: The wizard, Stredor DeGrey has made a terrible mistake. While working on a new spell, the wizard accidnetially opened a portal to the nine hells and was taken by the Bone Devil, Zalras. Zalras wants to use the wizard's ingunieity to construct war machines to expand their territory. The heroes have been hired to travel to hell, rescue Stredor, and return him to the material plane. This adventure for 4-6 players of 11th level sees the players making their way across the blasted wastes of hell to climb Zalras' tower an rescue Stredor.