From the back cover:
Behold the Power of Chaos!
Last year Green Ronin Publishing gave devils their due in the critically acclaimed Book of Fiends, Volume One: Legions of Hell sourcebook, but the Lower Planes are home to evil every bit as ancient and potent as that of the Pit: the demons of the Abyss. Embodying chaos and evil, demons are frequent and unwelcome visitors to the Material plane. Armies of the Abyss, by Living Greyhawk Gazetteer author and Polyhedron editor Erik Mona, is your essential guide to the denizens of the infinite layers. Inside these covers you'll find:
- The Commanders of Chaos: Complete descriptions of 22 demon princes, including information on their personal realms and spell domains. These lords of the Abyss provide a complete pantheon for the powers of darkness.
- The Henchmen of Evil: Over two dozen new demons, including a new race, the Qlippoth. These fiends provide challenges for characters of all levels.
- The Thaumaturge: A new core class, a spellcaster who gains power through dedication to a demon prince. However, such power comes at a terrible price...
- Tools of the Trade: New clerical domains and spells for the Thaumaturge and other evil spellcasters.
- Abyssal Images: Stellar art from 3E concept artists.
Since the earliest days of roleplaying, demons have been the ultimate opposition of fantasy adventurers. Do your players have what it takes to defy the Abyss?