Interesting lore and stat block updates to overlooked monsters, with new monsters that don't contradict the original lore but provide minions for the powerful and mysterious Gehereleths (Demodands). The supplement leans into the warden aspects of the gehereleths, and opens up the possibility of a gehereleth-cetnered cult based in a prison. Overall, great supplement. Get it if you are interested in planar campaigns or want another layer of depth to an Avernus or other fiend-centered campaign.

This book is very helpful! The author understands that running ten attacks in a single turn is difficult, and it adds an interesting subclass. We can always use another warlock patron! And the rouge modron race works really well for planescape settings.