Stygia

==== Are there any sources which have (at least somewhat) detailed information about general locations in Stygia other than Ankhwugat or Sheyruushk? I found something called the Black Kingdom on the internets on which I can't find any info.  ==== I assume you mean other than the diabolical holdings, since those are obvious. I don't find any reference to a "black kingdom" that pertains to Stygia the D&D planar layer. Some infernal locations can be found in FCII. The only divine realm other than those you know is The Steadfast Chill, realm of the Cerilian goddess Kreisha.

And if there are no significant sources, do you have any suggestions on what canonical information not to run afoul of while creating new territories?
Levistus is in charge, Geryon used to be... not sure what you could really get off center here, as long as you remember it's by and large a friddly cold place.