These are Deurgar Dwarves (aka Deep Dwarves). They live far beneath the mountains and are the more sinister of the Dwarven kind. They, like their Mountainous kin, are shorter than the Hill Dwarves since they spend more time underground than above it. in fact, less time above ground than even the Mountain Dwarves. They aren't very freindly and value magic and even psionic power more than their other kin. They are also known to support slavery more. But, not all Deurgar are bad apples, it's just that their culture is bent that way. They're not very popular with Mountain Dwarves at all, but Hill dwarves don't care much so long as the individual is not with a raiding party. Humans and other races have little knowledge of them so they just think it's a weird gray dwarf and don't think much after that. For this reason there have been some Deurgars that walk in and out of some societies with ease. But lethal bar fights always start, to the confusion of others, when a Mountain Dwarf is present.
As far as looks go, they are gray skinned and bald, except for males, they have beards. Their eyes are pale and slightly glow with an eerie pale light. Like all dwarven-kind, they are stalky, durably built and their women are busty (I don't know why but I never complain).