This area could be a epic level multi-layer dungeon that starts as an extension of the underwilds. It could be for levels 25-30 as the UD could use some more epic level dangerous areas for mid to high epic levels.
The following is the excerpt from the "Forgoten Realms Underdark" resource book.
Cairnheim, Demesne of the Dodkonk
(Upper Darklands)
The stone giant villge reeks with the stench of the undead, ruled by a stone giant lich called the Dodkong, this "kingdom" has few residents, but even a handful of stone giants can level a town or scatter a copany of hman soldiers. The Dodkonk sees no reason to conquer new territories when his effective rule through fear extends far beyond the series of tall caverns where his stone giants dwell. The residents of Cairnheim spend their days hewing out precious stones and carving rock into crude art.
Carnheim (village): Conventional (Monstrous); AL NE; 200 gp limit; Assets 5,460 gp; Population 546; Isolated (stone giant 96%, undead stone giant 4%).
Authority Figure: The Dodkonk (male lich stone giant sorcerer 10), master of Cairnheim.
Important characters: Ruvok Aerthmett (female stone giant expert 6), royal artisan; Koenig Serptenspine (male undead stone giant ranger 9, Chief of the Dodforers.
Warriors: Any adult stone giant is a competent fighter, and many of Cairnheim's giants also have levels in barbarian, fighter, or warrior. Cairnheim is home to about 260 adult stone giants, plus 20 doforers (or "Death Chiefs"), a special kins of undead stone giant.
Cairnheim extends from just beneath the surface in the Giant's Run Mountis to a depth of approximately 1/2 mile. The village is spread out through a winding series of lava tubes and caves, which surprisingly required avery little modification to be comfortable for stone giants.
Though the cavern system constituts the boundary of Cairnheim proper, the Dodkong claims a much larger region in his heart. He considers everywhere that he is feared as his realm. He does not outwardly manifest this claim by planting flags or bellowing his kingship; he simply expect to be obeyed in a much larger area then he directly controls. In addition to this stone giants, the Dodkong also commands an unkown number of hill giants in the region and also reieves tribute from nearby human communities.
The dodkonk has sexisted for at least 1,500 years. Conservative but crafty, he uses misdirection as his prinsipla tool. Rather then exercising brute force, he prefers to turn his enemies against each other and thus weaken more than one foe at once.
When on of the clan chieftains in Cairnheim dies, the Dodkong brings him back to unlife as a ddoforerer, using ancient giant rituals nd the power of the crown of Obadai, a stone giant artifact that grants the Dodkong power over the undead. The dodforers are old and wise, but still yonger than the Dodkong himself.
Trespassing in Cairnheim, or in any place that the Dodkong claims, is punishable by death. However, the Dodkong clings to an ancient, little konwon giant custom that requires him to give aid for three days to anyone who requests it. He does not advertise his adjherence to this custom because he doesn't actually want to offer hospitiliatiy, but a character can recall this piece of information with a DC 20 bardic knowledge check or DC25 knowledge (history) check. Those who involke the ancient custom receive beds, food, water, wine and minor healing at no cost, instead of instant death. At the end of the third day, wise visibors are at least a stone's throw away from the Dodknog's claimed realms.
Sometimes while visitors are staying in Cairnheim, the Dodkong asks a favor in return for his hsopitlity. This in not technically part of the ancient custom, so he presents it as part of the gracious guest's duty. Those who deny him what he asks do not receive hospitality a second time, even if they require it, and they might "accidently" misjudge the passage of three days in the lightless Underdark.
Brief History:
Long ago, the giantish realms of Nedehim controlled the Giatn's Run Mountains. Its artisans and egineers carved great roads and stairs through the peaks and tremendous halls beneath the hills. Nedeheim was destroyed in -5350 DR by the armies of High Shanatar, and the giantish realm was reduced to a handful of scattered clanholds that soon became reclusive and backward.
In -160 DR, the Dodkong appeared from the dark below. He has never discussed either his origins or how he came to hold the crown of Obadai. But on his arrival, he gathered the stone giant clans of Nedeheim that thd fled into the Underdark 5,000 years earlier and forged a kingdom from them.
Since that time, Cairnheim has grown slowly. More than 500 stone giants now inhabit the village of Cairnheim, which is located in a high mountain cavern in the heart of the Giant's Run. More then a dozen minor clanholds of sone and hill giants throughout the mountain range acknowledge the Dodknog as their rler. several large tribes of orcs and hobgoblins would also answer the Dodkong's call, if the undead giant chose to muster the hmanoids to his banner.
