Archdevil Aspect Questions

[OniTenyu]

So me and my group are playing a campaign set in the nine hells, and have come across an issue we cant resolve.

In the book of nine hell's on page 141 it states aspects can not survive on the same plane as the archdevil, but later under Dispaters knowledge check description it states he sends his aspect to converse on the ninth layer, so can aspects exist in the same plane as the arch devil or was that a mistake?

[Twilightwyrm]

It was probably a mistake, but likely because someone confused "layers" for planes. So, either rule is as a mess up, or change the text on 141 to read "layers" rather than "planes". That, or assume Dispater exists in his own private demiplane.