Also known as the Cataclysm, the Upheaval of Elysium forever changed the face of reality marking the change of the world as a place of science and reason to a magic and pseudo-science.
The technology used to power the 12 lost cities of Pureblood man was both infinite, completely clean and unbeknownst to its creators infinitely dangerous. 11 of the 12 were connected via conduits much akin to the same tunnels that create the transit system each providing a backup to the other so that no city should wholly fail.
As the millenia passed the unbreakable conduits began to break as the world continued to slowly shift this multiple breakage in the power linkage caused the reactors to err, then Center 05s reactor went critical, the resulting explosion obliterated every Replicant and fresh Firstborn and the the island nation that was its host.
Mankind, though long passed, had already conceived a solution, a solution abandoned for reasons unknown to the replicants and unrecorded in any accessible archive. the center of that research being at devastated Center-05. At Center-05, 07 and on Forever Altered Luna, prototype 02 class reactors were in place and nearly functional, as well as at Center-07 14 incomplete devices known as Ether Conduits were discovered and finished and installed following the schematics laid out ages before.
Slowly the class 02 reactors were brought online, and all was well. When the Ether Conduits were activated the system thrummed power, and all seemed well until it was not, in a horrible instant all 01 reactors were ripped from reality with the entirety or most of their Centers. leaving behind the Canyons such as the one where is in modern day the holy city of The Church of The Firstborn. The class 01 reactor on Luna That Was mauled the moon leaving the iconic face forever unrecognizable. The world the synths had made for their firstborn was plunged into darkness and ignorance as the masters that had led them into existence were no longer present and offered guidance no more. On the wracked surface it was a brave new dawn the Firstborn were thrown into wild devolution and all knowledge was lost in desperate struggle for survival . Once again Mutogenetic storms swept the surface of the wracked world. In caves and remnants of the old world the fortunate now dwelt carving their memories into the steel and stone of their sequestered dwellings, whilst the less fortunate were condemned to mutation and savagry as the worlds death knell sounded its strange rebirth. Trapped in powerless halls and lightless chambers the bulk of the Council and Attendants that survived the implosions and the resulting devastating damage to their world surmised none of the First Born could have survived the catastrophe that had made the surface unlivable again. So in deep vaults and hidden chambers they waited, Emergency Reactors consuming anything in the old cities not of value to the Created.
DESIGNER NOTE
I think it important to alter the face of the moon in such a manner that it is not recognizable it will be a dead giveaway as to the planet being earth, and I've plans to send the player as a end game exciting run to the Reactor class 02 is and attendant staff (still thinking on staff, synths, actual bots, mad G.I.) from this lofty point it would be badass for the earth to come into view during a critical point.