From the Publisher's Website:
Demons and demon lords for your D&D campaign.
Unleash the hordes of the Abyss!
Demonomicon presents the definitive treatise on demons and their masters, the demon lords. Whether you’re looking to introduce demons into your D&D campaign or plunge your heroes into the heart of the Abyss, this book has something for you!
More than just a maelstrom of chaos and corruption, the Abyss is an exciting D&D adventure locale for paragon- and epic-level heroes to explore. Within its many layers lurk powerful demon lords and fiendish hordes eager to be unleashed upon unsuspecting worlds. This tome brings demons into the world of D&D, updates classic demons to 4th Edition, provides statistics for various demon lords, and introduces dozens of new horrors from the abyssal depths. It gives Dungeon Masters ready-to-use encounters and mechanics to make demons exciting elements in their home campaigns.