City of Skulls
The City of Skulls is a Carl Lynwood Sargent adventure module for Advanced Dungeons & Dragons, levels 9-12. This takes the party in a mission through Dorakaa, capitol for Iuz' empire in the From the Ashes revision of Greyhawk. You need to extract a Furyondy asset therefrom.
Also, the title is stolen from a Carter / de Camp pastiche of Conan. So it has no right to be good. But it is good.
As Boromir would warn us all, you cannot simply walk into a whole city of demonic enemies and KICK @$$. You have to use stealth. In Dorakaa if you let yourself be known to the authoritaahhhs you gain Notoriety. Eventually you get caught, and screwed.
Sargent would use similar mechanics for Night Below before he, er, left this hobby.