Duergar

Duergar are a type of dwarf but their skin is grey and they prefer volcanic areas
Distant kin to dwarves, duergar are a sullen, covetous race tainted by an association with devils and infernal magic. Known also as gray dwarves, duergar share a love of mining and metalwork with their dwarven kin. Most at home in the lightless depths of the foreboding Underdark, they despise virtually every other race in existence. They hate dwarves above all others, though, and will ally with other creatures temporarily if it means a chance to spill the blood of Moradin’s children.
Duergar resemble their Dwarven cousins, but they stand slightly taller on average and tend to weigh more. Their skin is grey to sooty black. All duergar have fiery amber eyes. Duergar beards and hair conceal long, stiff spines that carry a burning venom due to their infernal ties. They can pluck and hurl these quills like daggers. Their weapons and armor often depicting leering, demonic faces, images of rival creatures being executed, and similar ghastly scenes meant to demoralize opponents.

Duergar have a well-earned reputation as slavers. They rarely perform exhausting or risky tasks, relying instead on the work of slaves. The Duergar recognizes the value of slaves, though, rarely tasking them with jobs that are deadly or unlikely to yield a high reward. Most Duergar slavers capture only those who exhibit physical prowess or exceptional skill. The Duergar has no interest in enslaving the young, the sick, or the elderly; such individuals are often left dead as a result of Duergar raids. Usually, a large number of slaves are overseen by a small number of Duergar taskmasters. When the slaves are not working, they are treated like prisoners. A Duergar keeps its slaves in defensible structures, discouraging outsiders from attempting to rescue them.