The Book of Fiends (2003)

From the publisher:

Devils, demons, and daemons--these are the ultimate servants of evil. Learn all their foul secrets in the Book of Fiends, the definitive sourcebook on these fell creatures. This tome collects Green Ronin's critically acclaimed Book of Fiends, Volume One: Legions of Hell and Book of Fiends, Volume Two: Armies of the Abyss sourcebooks and combines them with the long awaited treatment of daemons, Hordes of Gehenna. All the fiends have been updated to the 3.5 rules, and the material on demons and devils has been revised and expanded. Details on the plane of Gehenna, its rulers, and inhabitants are also revealed for the first time. The Book of Fiends is jam-packed with evil for your campaign, including:

* Over 130 daemons, devils, demons, and other creatures of the Lower Planes, illustrated and with complete 3.5 stats.
* Monsters with CRs from 1/2 to 40; there are foes for characters of all levels.
* Brand new devils and demons that add to the classic fiends of Legions of Hell and Armies of the Abyss.
* Two core classes, the black-hearted Thaumaturge and the dreaded Unholy Warrior, complete with Epic-level progressions.
* Info on the celestial choirs and the fallen angels.
* Inspired illustrations by top artists like Sam Wood, Raven Mimura, Dennis Detwiller, Toren Atkinson, and Brian Despain.
* Details on the nine Lords of Hell, the seven Exarchs of Gehenna, and a plethora of Demon Princes.
* 4 infernal prestige classes for servants of Hell.
* A handy index by Challenge Rating.
* A bonus appendix by Enkwell Press detailing two cities of the Lower Planes.
* Ties to other popular Green Ronin products, such as the Book of the Righteous, the Avatar's Handbook, and the Unholy Warrior's Handbook.

The Book of Fiends provides profoundly evil foes your players will never forget.