FFG was seriously mistaken and at odds with canon when they said dwarfs don't mutate. I added that back into my house rules.

Anyways, someone pointed out that chaos dwarfs were covered pretty well in Warpstone 28. Here is a link to the additional material for your entertainment. http://www.warpstone.org/pdfs/warpstone%20previews/28/WS28_Chaos%20Dwarfs_Extras.pdf

From the Book Gotrek and Felix. The Lost tales. They only mutate under extreme chaos conditions.

That's what I recalled it from as well..that and "Drachenfels" with the mutated dwarf. Was there ever a Chaos Dwarf's novel?

jh