From the PDF introduction
A Web Enhancement for Fiendish Codex I: Hordes of the Abyss
With all the nastiness inside Fiendish Codex I: Hordes of the Abyss, and all the nastiness that the designers of the book couldn’t quite squeeze into this tome, you’re bound to have a bit of overflow possibilities. Our second installment of the aspects of demon princes introduces you to the queen of the succubi and brings back the aspect of Orcus from the Miniatures Handbook. He is a little changed in this version, but not very much. This part also introduces ancient Dagon, the first obyrith demon prince of this collection. As in the first web enhancement in this series, each aspect has entries with suggestions on how to use the aspect in the EBERRON and FORGOTTEN REALMS settings.
Obyriths are older demons than the tanar’ri that have arisen in the past millennia. Before delving into the demons themselves, though, take a look the information on the obyrith demon subtype in the sidebar.
This item shares the same name as the web enhancement for Fiendish Codex II: Tyrants of the Nine Hells. Fiendish Aspects II