Long before the first cells on earth had even emerged out of primordial ooze, The Zroni thrived as they were blessed with the power of the shroud, none knew then, that such power has a heavy price.
One scientist of theirs saw that their reckless psionic use had expanded the supermassive black hole in the galaxy to an insurmountable level, thus, civil war broke out between two factions, those who were wise enough to follow the words of the aforementioned scientist and those who drowned on their very decadence as the shroud answered to their will.
Before long the catastrophe their civilization wrought on their empire, and thus the whole galaxy became too much to bear, those drowned in decadence were absorbed by the abhorrent creatures of the shroud, making it unstable and dangerous. The last vestige of The Zroni made a ring world and they brought seeds from multiple worlds and planted it across the ring world itself.
Before they were finished, their souls were taken by the hungry abhorrence of the shroud, and thus, the seeding was incomplete. Many other alien race encountered sanctuary but were forced to flee from The Zroni defences.
Eventually, many lifeforms evolved on the ring world that would later be called Teyvat by the inhabitants.
One of those lifeforms were the ingenious and creative humans who made use of the abundant zroni crystals, of whom they call gnosis for the greater and visions for the lesser, not only that, but the abhorrence of the shroud left a shard called delusions, powerful yet inherently corrupting, it was locked in vaults across the worlds.
Before they can even take their place upon the stars, the ancient platforms of The Zroni rotted and invaders who had long sought after the system invaded. Humanity was brought to a low, and the aliens constructed beings similar to them to lord over, but then there were multitude of external invaders who brought even the alien empire to a low, giving the last of their will to their creations to lord over humanity for eternity, of whom none knows what for but themselves.
Those creations took multitudes of gnosis and visions from the weakened humans, but they did not know the locations or even the existence of delusions.
Thus, they lorded over them from a platform above the skies on the one remaining functioning ring world, they ruled as tyrant deities to humanity who had no cboice but to worship them.
Khaenri'ah was created by the remaining free humans who fled to the opposite of the ringworld, to the uninhabitable metals upon which they created technologies to protect themselves from the rotted Zroni tech, dreaming to one day, escape to the stars, away from celestia, as humanity were oppressed under the boot of the creatures, one by one, they forgot their advanced roots, and reverted back to primitives.
What the Khaenri'ah denizens didn't know however, that their freedom was going to be lost forever, one day, the celestia creatures discovered the free kingdom and plotted an invasion so great, it would twist humans to abhorrence, known later to be abyssal creatures and even changed the most loving of archons to one beset to challenge celestia itself.
It was at this point that the twins, Aether Lumine encountered the head of the celestia creatures, whom called itself the sustainer of the heavenly principles after witnessing the horrific massacre and corruption of Khaenri'ah and trying to jump to another world before being stopped by the aforementioned sustainer, and thus separated across times.
Now, as Aether took his first sight for the first time in 500 years, he awoke to see a new world, memories forgotten, too horrific to remember, thus, he took the first steps in finding his lost sister.
Will he succeed in finding her and escaping? Only time will tell.
Author's Note
Welp, thought I had to redo that one ever since I discovered sanctuary in stellaris, I kinda wonder what if Teyvat take place in such a thing? It wouldn't be completely out of logic, I hope you like this, updates won't come for the next foreseeable days, kinda busy with work nowadays.