(Written to be a primer for the players before the campaign begins. This place will be pure nightmare for the PCs. I've got a reputation to uphold for being a devious S.O.B. at times, and it wouldn't be one of my games without the promise of hardship for the PCs.)
The Necropolis of Voor is haunted by mystery. From its practical origins as an interment site for the extinct Voori race to the legends of the incredible fortunes it hides, it has captivated the minds of the more adventurous in Antediluvia for centuries. However, no one enters the Necropolis without fear being foremost in their mind. It is said the mountain itself is alive, that it can sense intrusion and repel it with its defenses, which are said to include the bodies of the reanimated dead, traps, and the remnants of Voori sorcery.
What began as a mountain-top cemetery for the honored dead of Voor grew over thousands of years to encompass the entire outside surface of the mountain. The Voori began to build monuments to house their dead after this, building on top of the graveyards of old. When the monuments began to fill, it was decided that a complex must be designed and built within the mountain itself to house the bodies of the dead to come. Centuries passed as the project commenced and was completed, but in the process the Voori discovered, hidden under the mountain, secrets of dark sorcery and the dark masters that ruled them until they disappeared completely. No one knows what these masters were or what sorceries were taught to the Voori by them, but certain hieroglyphs found within the first several levels of the Necropolis mention them in passing.
After the discovery of their new masters, the Voori were taught their secrets, which may or may not have been limited to the worst sort of sorceries. Mention has been made of strange technology found within the pits of the mountain. The Voori came to dwell entirely within the mountain, caring nothing for the outside world any longer, wanting only to worship their masters and learn their secrets. Their sizable nation fell into discord and ruin, leaving no legacy other than the Necropolis and a few places in the wider world named for them. They disappeared from the earth, and only recently have the Necromancers of Naat found evidence of Voori activity again after many centuries, but they have noted that the creatures calling themselves Voori today are no longer of mankind.
It bears note that the Necropolis attempts to claim those who enter without permission. It sends dark messengers of various sorts after those who pilfer the dead that rest there, and very little is known of the interior other than what the Necromancers have uncovered and brought back from the tombs, and only that which (as relates to physical objects) the Necropolis did not send its messengers after to retrieve (resulting in the deaths of the interlopers in nearly all cases). It is these expeditions that have returned with horror and rumor as their only treasure that have fired the ambitions of many adventurers in the lands near the mountain, but few have actually dared to delve the Necropolis. Those who live in the surrounding country avoid traveling too near it at all costs, and consider those who wish to plumb its depths foolhardy or insane.
However, the lure of riches is strong, with some strong enough to ignore the warnings. For those that the promise of treasure does not snare, there is also the rumor of rare knowledge secreted away below the mountain by the Voori of old. The Necromancers of Naat have laid near-exclusive claim to finds in this regard so far - and most have escaped with little else but their lives and memories intact and live in fear lest the mountain send something to claim what they took, tangible or otherwise.