The creators of the Black City, the Ancients, were this world's first users of magic. Vancian magic, as established in Tales of the Dying Earth, presupposes a time in the distant past when science was greater, and wizard-scientists created the myriad arcane formulae that got passed to succeeding generations as spells. The repertoire used by the wizards of the world is a paltry thing compared to the wonders of the past, and the ability to create new magic is limited by comparison in this day and age.
The Ancients were scientists and wizards; they experimented on simpler forms of life and created the automated spawning vats that continue to release aberrant creatures and monsters into the world's dark foundations.
Since the fall of the Ancient's civilization, the primitive human slaves kept by the Ancients have devolved into atavistic cannibals, like the morlocks of HG Wells. The dungeons of the Ancients - alchemical labs and holding areas - are still maintained by bizarre automatons and servitors, created in the image of the Ancients themselves, the way we might create an anthropomorphic robot.
Deep in the dungeon lies the final secret of the Ancients and the reason their society fell. Perhaps their descendants live there still, devolved and bestial. The remnants of their race lie dormant or hibernating, a plague on the world of men just waiting to be awoken or released.
Who are the Ancients? I have two candidate races in mind, please vote on the poll on the left (if you don't mind helping me decide).
If Lovecraft and the weird fiction authors lived today, I have no doubt they'd embrace ufology; but since they're gone, I'll do it for them. The Greys were exiles or colonists from another world or another dimension that brought their alchemy and science with them. Perhaps in the depths of the city lies the remnants of their colony ship, fueling the city's systems with a perpetual energy source.
They immediately set about tinkering with terrestrial life to ensure they had the slave races and food they needed; as psionic masters, there was little reason to fear a slave revolt.
Their servitor constructs will seem tall and spindly when compared to traditional golems, with six arms and large, oversized heads, and bulbous eyes. Only in the depths of the dungeon would player characters discover the truth.
It's said, in the far future, the descendants of the Greys will rediscover the world, and begin abducting the humans of that era to determine the extent that the human genetic code was crafted by the Ancients. The truth is out there.
The other source for the Ancients would be from the world's distant past - 65 million years ago, in fact, when the Saurian empire ruled the world and domesticated or quelled the dinosaurs. Evolved from Troodons, these bipedal dinosauroids mastered the magic sciences and alchemy, but brought doom upon their civilization when they summoned the dread star Nemesis and created a world-wide extinction event.
The greatest of the Saurian sorcerers weaved a master ritual that wiped the dinosauroids from the fossil record but hurtled a portion of their civilization forward in time, to rebuild in an era free from the baleful glare of the death star Nemesis. Thus was the Black City created.
The Saurians use pylons and matrixes and store their information in elaborate crystals; it's said their libraries are full of crystal skulls inhabited by the psyches and knowledge of the ancestors.
As the world grew cold, the Saurians retreated to a hollow world cavern deep beneath the city, where they established a nuclear sun and populated the place with altered forms of terrestrial life. Over the eons, the Saurians have devolved into vicious reptilian monsters that can no longer use their own pylon technology; from time to time a mutant is born with a glimmer of the intelligence of the Ancients and the ability to commune with the crystal skulls of the ancestors.
Their servitors and automatons continue to maintain the systems beneath the frozen city, scanning the night skies for the return of Nemesis.
Perhaps the Ancients themselves are still there, hibernating in the deeps and waiting for the time when the world is steamy and hot again.
Just who do you think continues to propagate the belief that global warming is a myth and we should continue burning our fossil fuels unabated? Who stands to gain when the poles melt and the world returns to a hot, humid atmosphere?
Definitely won't be your typical D&D campaign. I can't wait to unleash Vikings on this place.
Please vote if you don't mind - The Greys exude an alien weird horror vibe and would be a shocking reveal as the secret masters, whereas the Reptoids are a nod to Land of the Lost - one of the cooler TV shows when I was a kid.