Why do people worship devils anyway? Mostly, it's for the quick fix, the power offered immediately, with the price, a terrible price, to come later. Certainly within a fantasy world, however, it's possible to conceive of people who choose this path just as others choose to worship more mainstream (and dare I say 'good') deities from the regular pantheon of gods available in that world. This book is for those DMs, and players, in whose worlds this is a possibility.
While the worship of so-called 'evil' deities is common amongst the monster races, those devotees to be found amidst more civilised groups are likely to be very circuspect about their religious tendencies - if a horde of adventurers doesn't deal with them in short order, inquisitors sent by a mainstream 'good' religion or an angry mob of locals are likely to be kicking in the door. So such worship will be done in secret.
For that matter, the devilish deities themselves may be acting covertly, to attract people who would not normally in the course of things choose an evil deity, but who may be seduced away from good - perhaps by powers selected to enhance their success at profession or in life, innocuous-seeming at first and only being revealed in their true horror later if at all. This, along with details of how fiends of different alignments may behave, is explained in the first couple of pages of the book.
We are then treated to detailed descriptions of several potential demonic deities: Ishale, Demara, Minakhta, Badenoch, Aatxe, and Wealhta. These are regarded as major examples of demonic deity, and each is treated in considerable detail including material about both the demon itself and the sort of cult that might grow up about it - complete with an example temple mapped and described in sufficient detail for a party of adventurers to deal with the problem. Typical minons, followers and monsters associated with each also appear.
If you choose to base a campaign around the hunting down and eradication of worshippers of evil, this book could provide a good starting point, with five complete cults to deal with. Each of the worship sites described has sufficient detail and background for you to build an adventure around seeking it out and then mounting a raid against the temple and the worshippers using it.
There is also a clutch of minor devilish deities, a new prestige class - the Spineless, a creature who is able to wiggle through the smallest hole - and new spells for the War Domain, whose death and destruction are popular with many of the deities herein. All of this serves to add flavour to a whole new area of life which can be mixed into your campaign. Will your players become champions of good, seeking out these cults wherever they may be find... or will they themselves be seduced and led astray?Rating: [5 of 5 Stars!]