The first empire of man was the Khufic Empire: god-kings built temples to themselves for a housand years, turned pasture to desert to glass with their wars, and pierced other worlds with the stolen lore of Nemesia and of Kythera Antigua.
It fell, utterly, its idols thrown down and its lines of kings ended. The war of its dying spread like wildfire, and whole towns were burned with arcane fire or deprived of every living thing by poisons or curses. Its kings retreated to their tombs to lick their wounds, sealed them with spells to last a thousand years, hid or lied or died to live again. Today, a hint of the black lore of Khuf — look no further than he Lord of Worms! — can shake the world. Imagine it at its height!
So: why did Thrane win?
Because of Eru Ilmater, and because of the Celestials.
Eru Ilmater was a priest of the Old Gods as all his father’s line before him: he knew to placate Qhlu for a childbirth and a harvest, he knew the prayers to Vor for safety from brigands and thieves, he knew the way to invoke Luth and beseech Abrys and avert the Great Old Ones. He had apprenticed in Kytherosnas a physician-priest at the court of an Ifrit grand-merchant who dwelt there to heal the sick and the wounded, to shrive them, and to consign them to a life of eunuch soldier-slavery on Imix.
One day, he found an old man amongst the sick, feeble of eye and mind.
“Old father”, said the still-young Ilmater, “I will make you whole by the grace of the Salt God and the Earth Mother, by the ways of the Hidden One and the Eater,” and he did prepare to do so.
“No, Rose of Iluvatar, still thy orison. Thou shalt make whole the world entire: those who know thy name shall not suffer and die in vain but await thy return, ever and again, in new faces. For thou mentionst not thy siblings; not the Weaver nor the Wild nor the Worm, and yet thou werest once of their number and shalt be again.”
And this was the last word spoken by the man, for he fell away and revealed a spirit of light, to declare Eru Iluvatar the First Prince of the Cathulian Church. They did flee into the desert, and found followers in the hidden places and the old places, and did teach them in the holy ways. Other Eru came, apostolic and guided, angels appeared with gifts and intelligence for their chosen people. Iuz was their first, a mercenary soldier and great tactician, shining with zeal.
Now: the departure of so many and the mustering of a new army greatly upset the pharaohs and sorcerors of all Khuf. They did raise dragons, and armies, and mercenaries. They did send ambassador-assassins, dancing spies, soldiers whose guts were rot and filth. They did send seven times seven plagues of death to the camps of the Iluvatar, but almost all were turned away, and the armies of Eru grew.
Iuz, the trusted general in the armies of Eru, called Ilmater to meet secretly in the Abyssian Tombs. While the Celestials warned Ilmater that a trap awaited them, Iuz himself was the trap, and Ilmater was bound in thorns and sent to the Iron City.
After decades of bloody war, both sides ground to a halt: the empire of Thrane with the Iuzant at their backs across a deeply treacherous desert, and the Iuzant isolated. The twelve princes of Thrane mourned the passing of their great martyr, and await his return.
And what did the Celestials want with Thrane at all?
They beheld a world which, if led by Khuf, would soon pierce the gates of horn and bone, and freely wander all the worlds. They beheld a world where human power, untempered by wisdom, would spill forth and damage their great star-spanning experiment. But! If those same humans could be taught, they could become a paradise.
But, paradoxically, they found themselves unable to directly force the paradise into being; after a certain point they were unwilling to act directly: the Iron City might, but not the Golden Throne.
Realistically, they just can’t. On the one hand, Celestial resources are less fluid than usually believed; there are a limited number of solars and their duties are prohibitive. On the other hand, to force a paradise upon nascent humanity wouldn’t work; they had to be ready for it and commit to it.
Thrane is their experiment in building a paradise.