Van Richten's Guide to Demons (Item)
From Mistipedia
Fiends Treated
The Black Duke: This fiendish cult leader briefly terrorised the Ehrendton in northeastern Nova Vaasa. Cult members spouting heresy to the effect that the Black Duke is an avatar of the Lawgiver are arrested, tortured, and executed from time to time. [VRGtD, Author's Notes to VRGttM]