They say that Khalgorond is the oldest city in the world. It was not built by men, but by cyclopes. Men struggled to tear down the ruins of the old city, and narrow the roads built by giants. The stairs are motley, and the original, immense granite blocks contrast with the smaller, inferior stones set down by men to make the strides manageable.
When the cyclopean mummies were unearthed, King Kavangules (rhymes with 'Hercules') believed it to be a great blessing. He ordered their heads cut off and paraded them through the street. The three heads babbled and moaned, their black tongues lolling in their mouths. The king ordered his wise men to decipher the mad ramblings of the mummies, for amid the madness there was wisdom, or so his people were told.
In those days, the history books were corrected, and the erroneous ones burned in the squares. Smoke and steam rose from the palace, evidence of the new inventions that were being forged (such as the two-wheeled mechanical horse). It was, by all accounts, not a bad time to be alive.
And that is the only part of the story that everyone can agree on. They send their children to bed, before they tell the next part.
The king learned the language of the mummies. He would spend hours conversing with the corpse-things. He had three small, marble thrones built for the heads, which were erected beside his own throne, so that the mummy heads could be present when he announced his judgments. When he wished to quiet their murmurs, he gagged each one with a golden ball.
King Kavangules learned the language of the cyclopes. He no longer spoke the tongue of his nation (Bosh) but instead addressed his court only in the Cyclopean tongue. He demanded that he only be addressed in the same language, and took a Cyclopean name for himself: Chem-Shemaat.
The king entertained foreign necromancers, and showered them with gifts. He met with the misshapen sorcerers from the Darklands, and could be heard laughing with them until the small hours of the morning. He had new chambers excavated beneath his palace, and killed the builders for secrecy.
He later grew abhorrent of his eyes, and refused to remove a blindfold, upon which was painted a singular blue eye. He demanded that all of his household remove their right eye--in such a way that the eye was undamaged--and place it in a golden bowl in the temple, towards some undefined end. Many of his servants obeyed, and his slaves had no choice.
It was at this time that many of his staff began to flee, and the first whispers began that the king was going powerfully insane.
He ordered the bodies of the cyclopean mummies retrieved and reaffixed to the cyclopean heads. Thereafter, the arisen cyclopean mummies could be seen shambling around the castle. They followed the king around like servants, and knelt at his feet. The king could be heard speaking the Cyclopean language to them; the mummies responded in kind. (In other retellings, the king merely speaks gibberish to the mummies, instead of any language.)
Finally, the king embarked upon a series of atrocities, of which no storyteller may speak of (upon pain of death, by decree of the Grand Magistrate). But the final atrocity was when the king demanded that all of the newborns in the city of Khalgorond be delivered to him for an unspecified purpose.
Over a thousand infants had been delivered, and the palace was filled with the sound of crying infants, when the populace revolted. The mob was quickly joined by the army and the town guards, who stormed the palace. The king's most loyal warriors were overwhelmed. But although the sound of crying babies never ceased, the revolutionaries never found a single one.
The king was found and captured, but the cyclopean mummies emerged from unwholesome shadows. Fire flashed from their eyes, and their claws rended men's souls. Darker things emerged from the dungeons, and gorged themselves on the entrails of peasants. The skies rained filth.
In the end, the revolutionaries were driven back out of the palace. Rather than lay siege, they decided to seal the king inside the castle. For blocks around, the buildings were dismantled and hastily used to brick up the entrances. The king and his mummies did not oppose this, since they were (seemingly) only interested in securing the interior of the palace.
Over the next month, more stones were added. Eventually the sounds of crying infants ceased and were replaced with new sounds: vast claws scratching and tearing the mortar from the seal.
Priests were brought in. The stones were consecrated. Finally, a formal construction project was begun, to entomb the whole palace under a pyramid. It took six years, but the pyramid was eventually completed, laminated with anti-undead enchantments, and was decreed to be so secure that the king (should he live) nor his mummies ever be able to burrow their way out, not even if they should spend a millennium in labor.
Eventually the city of Khalgorond was swallowed up by the desert, like much of Abasinia. The city was abandoned, as the population moved closer to the coast.
Over time, a new curse settled on the place--anyone digging in the sand would unearth flames that spat and twisted against the wind. Or an excavation would suddenly exhale a billow of black sand and a cold wind would blow out, that rotted men's lungs in their chests, before the excavation would collapse in on itself. The city had become cursed, and it was then that men began calling it the Burning City, after the fires that burned under the ground.
But the Black Pyramid must still be protected. Against erosion, or foolish tomb robbers. And someone must always be listening at the stone for the sound of something slowly scratching its way up through the stone.
And so this is the fate of certain criminals in Abasinia: they are magically geased and sent to the Burning City to guard it from the world, and to guard the world from the Black Pyramid. These unhappy criminals live in the ruins of the old city around the Black Pyramid. Water is sparse, and food sparser, so they spend their brief lives banding together and murdering each other for scant resources. But they are even more adept at murdering tomb robbers, who carry much needed supplies and foodstuffs. It is a form of orthodox banditry, since the slaves of the Burning City will waylay all who travel the deep desert (except those who display an enchanted tughra of the caliph).
Many of these sad men succumb to the madness of that place, and pluck out one of their own eyes. They sleep in the shadows beneath the buildings, and watch from broken windows without blinking. Still, they do their primary job. No one has disturbed the Sealed Palace for almost a century. But they do not speak of the dull grindings that they hear beneath the earth, and nor do they whisper of the lights that shine though the black bricks on moonless nights.
I love rumor tables as much as the next guy. But what if players could find storytellers and pay them to tell stories about awesome dungeons? Like, I can imagine a party finding a storyteller and hearing a story that includes pretty much everything in this post. It doesn't have to be 100% accurate, but would it be fun to just sit down and hear a story about a dungeon, instead of collected fragmentary rumors?
Or, on the other end of the spectrum, the PCs might find a storyteller and pay him to tell them stories about other dungeons all over the world. Like, after paying the storyteller his gold coins and hearing The Story of the Black Pyramid, the storyteller might be like, "Ah, but you are adventurers. You must be after gold, and so I am sure you've heard The Story of the Zaris Malganum and the Walking Hands. No? Well, I will tell it to you. . . for my usual fee." And then you can set the PCs off questing for a dungeon half a world away just because they think it sounds cool.
Here's a picture of some actual decapitations, which I thought was powerful and informative and appropriate to what a PC might find inside the Black Pyramid, at least in theme. It's here for inspiration foremost, but also in the hopes that a DM will treat severed heads with appropriate respect and horror. Many people find it offensive. NSFW.