Ages ago I mentioned in passing (whilst looking at early WDs) that a blog post on Fiend Factory rejects that did not make it into the Fiend Folio might be worthwhile. After all when heavyweight, deep level uber-foes such as the Flumpf make it in, what was missing must have been really bad. And then I promptly forgot about it.
Anyway Greg Gorgonmilk has rised to the challenge and started a series of blog posts on precisely that subject. Go read them.