MitD XIII: Learning is happening

[Jasdoif]

FC2, at least, suggests the BoVD versions of Archfiends are "the real thing" and that the FC1 and the FC2 versions themselves are "very powerful aspects, but still aspects". Only a bit of work is required to convert BoVD fiends to 3.5.

FC1 explicitly says "Some of the demon lords described in this chapter originally appeared in Book of Vile Darkness. They have been updated to conform with the revised (v3.5) D&D rules." (There's also a little section in the chapter for increasing their stats to an arbitrary level for use in an epic-level campaign, but I think that's the book punting on whether there's an "actual" power level they have)