The following information is taken from the official DM's Guild entry online. 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! Demonomicon (2010), by Mike Mearls with Brian R. James and Steve Townshend was the fourth monster splatbook for D&D 4e. It was published in July 2010. Five demon lords make their 4e premiere in Demonomicon.