The Gehenna of Obsol
The Technocracy of Ull was destroyed so long ago that few historians agree when it ruled the known world. It's impact, however, has carried on through untold Millennia. The Ull created marvels that fused magic, machinery, advanced science, and reality-bending primordial forces into a Super-technology that made their small kingdom a paradise of leisure and study.
From their hidden cities, the Ull sent out emissaries riding giant constructs and guarded by biomechanical war machines. They offered machines to ease labor, spells to shape the land, and advice to lead an orderly, safe life. But at the cost of tribute, obedience, and by giving up their best and brightest to be raised by the Ull. Ullan Technomancers built marvelous automated temples where their gifts were manufactured and maintained by initiates. No outsider was permitted to learn how to make, repair or maintain Ullan marvels; only how to use them.
The Ull's client states chafed under the restrictions, and, in time, stole and reverse-engineered enough technology to build war machines to rival Ull's. And a war unlike any before or after occurred as an allianc of former client states attempted to conquer Ull and take back the generations of tribute and the knowledge they felt they had a right to possess.
Obsol was the site of one of the greatest clashes of the war on Ull. War machines, constructs, magicians, and even aliens horrors. The high mountain pass was reduced to a crater so full of dangerous wild magic that it was shunned for a generation. In time, the war-battered Technocracy turned the valley into a dumping ground for ruined war machines, failed experiments, and scrapped magitech.
When the World was Drowned, the Celestial College, an academy of sorcerers from the Grand Union were flooded from their home, they survived by shielding their entire academy in a magical dome. They lived for Two delegations under the sea, transforming from a school into a clan of magi.
The spells that held their home safe from the crushing waters above could not last forever, and in time, the Celestial College moved en masse in magical vessels onto the surface and set out looking for the lost city of Ull. The city itself was never found, but the vast magitechnological garbage dump of Obsol was.
Some of the lower-status families of the Celestial College chose to stay - to pick through the ruins and perhaps learn a few new magics, and to create a port of call for their wandering brethren. These Magi picked through the ruins learning at least a few of the mysteries of Ull for years before making a discovery that changed everything: a rogue faction of Ull had chosen the shunned Valley to serve as the site for a secret academy where they taught Ullman secrets to Magi if the rebel states, and within a doorway to a Demiplane where the Rogue Archmage Demal had built a massive mechanical Labyrinth outside time and space. Demal has bound an Elder Being, a proto-god that not only sustained his private picket dimension, but allowed him to manipulate the flow of time. At it heart, a weapon against even the gods, The Armageddon Clock sat, counting down the End of all Things.
The magic that the scavengers learned there far outstripped the Arcana of the Celestial College. Using the powers they learned from the Forbidden Academy and Demalion’s Atelier, they were able to build a gigantic clockwork city in the ruins of Obsol. Here their descendants are taught the secrets of magic and technology that bends time and space. Few ever leave, and guests are only welcome in a closed quarter in the harbor.
The rest of the Celestial College moved onwards towards where they thought Ull was buried and were never heard from again. Their fate hidden even from the Demalions' magic.