the "expedition to the ruins of greyhawk" adventure puts the adventuring party on a quest into the depths of the ruins of castle greyhawk to save the free city from the forces of the foul demigod iuz the evil - the half-fiend son of the demon lord graz'zt and the evil archmage iggwilv. iuz built a sinister empire that once held the northern lands of the flanaess in fear and constantly threatened the surrounding kingdoms in an attempt to rule the entire world of oerth.