The Dark Dwarves appear to be active in the Abelion Hills. They appear to be the only human group welcomed by the Demi-human tribes.
In the Web Novel, it appears the Dark Dwarves sell their craftsmanship and services to the tribes in the Abelion Hills. In exchange for providing metal arms for the frequent tribal wars, they receive demi-human slaves such as goblins, ogres and orcs.
Like mainstream Dwarves in the Dwarf Kingdom, they appear to be adept craftsmen.