Mongoose Publishing has continued its successful product strategy for the d20 market: instead of publishing scenario books with their inherently limited usefulness and shelf life, Mongoose created a range of sourcebooks useful to the DM in the long term. The first of these have been the Slayer's Guides, which expand upon the information found within the Monster Manual to give detail and depth to a classic monster. In the same spirit of expanding into new areas, Mongoose has begun a new series of sourcebooks. Entitled the Encyclopedia Arcane series, the books will focus upon different aspects of magic within the D&D rules. The first of these is Demonology - The Dark Road.

As with other Mongoose titles, this 64-page book is well laid out and lacks many of the typographical errors seen in other d20 releases. Some of the art is excellent, especially the illustrations of various Monster Manual demons and devils drawn by Eric Lofgren, Scott Purdy and Anne Stokes. A little of the remaining art is rather scratchy and drawn out of proportion, but it would be unfair to name the culprits!

As the title suggests, Demonology - The Dark Road expands upon the mechanics for summoning and binding creatures, more specifically evil outsiders, from their home planes. While the book's title suggests it covers just demons, the Chaotic Evil Tanar'ri outsiders, it actually goes further than that and lumps in their Lawful Evil counterparts, the Baatezu or devils in its coverage. Thus its discussion and examination of demonology is applied to both types of outsider, and in keeping with that, so will this review.

Central to this sourcebook are three new prestige classes, made possible by a singular idea: that the study of demons shouldn't be limited to NPCs. The assertion that demonologists are inherently evil, and thus the preserve of a DM's cast of NPCs, has been part of D&D from the beginning. In Demonology - The Dark Road, the doors to the art of demonology are opened wide to player access. The 'Dark Road' begins with the humble magic user summoning demons or devils, not for evil, but to gain access to power or knowledge that has been otherwise denied them. Instead of demonology itself being inherently evil, its practitioners are exposed to the evil nature of the creatures they summon. Thus, they might start as good aligned characters, but in their desire to learn more, demons will place temptations in their path that will set them on the Dark Road and see them corrupted.

The first of these Demonology classes is, fittingly, the 'demonologist.' As the demonologist grows in ability, his skills at calling and controlling demons grows, but the rules still contain a definite chance for mishap and even death if they fail. Beyond the basic demonologist, there are two even more specialized prestige classes. One is the 'binder,' who can summon and bind demons into objects, creating a unique category of magical items and even demonic artifacts (Elric's possessed greatsword, Stormbringer springs to mind, though its creation would be beyond all but the most powerful). The second prestige class is the 'possessed,' who summons demons with the aim of allowing them to temporarily co-habit the summoner's body and actually gain some of the demon's abilities.

These are three powerful prestige classes, because in addition to the abilities granted by each prestige class, the character actually keeps the advances in spell casting he would have gained had he remained an ordinary wizard or sorcerer. Thus a sixth level wizard/second level demonologist would be able to cast spells as an eighth level wizard and were he to gain another level as a demonologist, he would be a ninth level caster. He does not, though, gain the other abilities of a wizard or sorcerer; instead he receives those granted by the demonologist prestige class.

Not surprisingly, the mechanics central to Demonology are for summoning and binding demons. A d20 is rolled for both the summoning and the binding, modified by the character level of the demonologist and various situational modifiers. For summoning, the difficulty is determined by adding the CR of the demon that is being summoned to a DC of 10. Control of a successfully summoned creature is more difficult, being a battle of wills, in which the demon's CR is doubled and then added to a DC of 10. An unsuccessful attempt to control a demon is invariably perilous to the summoner - a summoned beast is an angry beast!

Much of the rest of the book builds upon and applies these basic rules and ideas. Thus the new feats are really only appropriate to the demonologist class, as they ease and speed up the summoning process. It is also likely that only demonologists will be interested in the new magical items given here, as they perform similar functions to the new feats. The second set of magical items is that of examples of those created by the binder prestige class, having bound actual demons into objects to empower them.

There no rules for the GM on how to control a player character demonologist's access to the various types of demons. Instead he is advised to maintain control through regulating the availability of the ingredients and information required to perform a summoning. Some ingredients are decidedly difficult and expensive to obtain, such as that needed to summon a Nalfeshnee of the Tanar'ri family. Its pentagram must be laid out using the powdered rope of a noose used to hang the instigator of a genocide and a golden mirror at least four feet high and costing 7000 GP be used as the summoning focus. Other demonologists and secret tomes will prove to be the source of the information on the rituals and summoning. Both these and the necessary ingredients could be used as the inspiration for actual adventures.

Nor are there rules for instructing demons, except to provide a word limit, which can be increased through level advancement. Again, there are guidelines and suggestions, but in general, Demonology - The Dark Road is low on rules and high on discussion and ideas. The last part of the book discusses the attitudes of various races found in D&D3e, including the drow, duergar and yuan-ti, before going on to detail the summoning requirements for each of the demons and devils to be found in the Monster Manual.

If I have one final complaint, it is that Demonology - The Dark Road is perhaps a little expensive at $13.99 for what you get, especially when you compare this with the prices for other d20 books of a similar length. That said, it is the perfect complement to Green Ronin's Legions of Hell, and will be useful to any DM wanting to expand upon the nature of summoning demons within their own game. DMs may choose to restrict the material found within Demonology - The Dark Road to just NPCs, but that would mean your players missing out on all the possibilities to be found within Mongoose's risky and rewarding new approach to the dark art.