The Abyss inspires all manner of evil and depravity in mortals, and not all of it is consumed by fire and flames. Among the fallen Dwarves, there exist those known as Chthonic Dwarves: warped beings who dwell in darkness and experiment with forbidden knowledge, twisting flesh and souls as easily as their brethren work iron and bronze.
When I chose the Abyssal Dwarves as a faction in Kings of War, I realized it would be an excellent opportunity to use some of my old Dwaves of Mid-Nor figures from Rackham Miniatures. While I don't have enough of these figures to make entire regiments, they still function well as heroes for "flavor characters" when mixed with other Abyssal Dwarf troops.
While I don't know the full lore for the Dwarves of Mid-Nor, they're obviously a twisted race of dwarves and so fit in with the Abyssal Dwarves. I decided on the name of "Chthonic Dwarves" for them, seeing them as an extreme subterranean sort with an isolationist (and perhaps cult-like) society. Where as the Abyssal Dwarves take the industry and militaristic aspects of the Dwarves to an extreme, the Chthonic Dwarves are more warped and focus on forging flesh and souls. From them come augmented troops, strange mutated creatures, and animated constructs.
I think the union of Abyssal Dwarves and Chthonic Dwarves will provide a unique spin on an Abyssal Dwarf army, and should make for an interesting overall look for the army!