any centuries ago, the duergar warlord X'all ruled over a mighty confederation of many tribes, which he forged into a single huge army to conquer the world. Invading from the depths of the Underdark, the duergar hordes ravaged many lands on the Surface before they were finally stopped and defeated by the dwarven legions of King Almi, who at that time reigned in the vast Dwarfrealm that is now ruled by his descendant King Kerrin.

X'all and his more powerful minions were no ordinary duergar, but were steeped in powerful magics of darkness and necromancy. King Almi and his council found that the duergar leaders simply could not be killed by violent means, and so they determined to imprison them in the hope that they would eventually die in captivity. To this end, King Almi commanded the building of a secure prison fastness beneath his realm, protected by traps designed by the most cunning of dwarven artificers and golems forged by powerful mage-smiths whose arts have long since been lost to dwarves. Here, X'all and his duergar lords were imprisoned and left in captivity as the years and centuries passed.

King Almi's hopes did not quite come to pass. X'all and his followers did indeed finally starve and die—only to rise again as undead, more dangerous and powerful than ever before. But as long as they remain incarcerated within their prison, they cannot threaten the world around them.