Whenever mankind gathers, sins gather with them. The Adversary, determined to break free of the bounds of Solomon's Seal, tempts mortals with promises of power and wealth. Hollow though these promises may prove when measured by eternity, many are seduced to its service. The Witch Hunters are what stands between the darkness and the light, even when such darkness is found in the hearts of mankind. Cities of Mystery details eight cities, 4 in the Old World, and 4 in the New. The cities' people, notable places, history and hidden threats are revealed in detail. Each local offers a suggested campaign for Grand Masters and new rules for Grand Masters and Witch Hunter's Alike.