Direct information about the Cataclysm is scarce, but its effects are still ongoing, and all too real to those in the Coalition.
What glories and wonders the the age of the Old Coalition wrought can only be guessed at, though it is known that it was indeed a time of greatness for the World- but its time had come. Surviving fragments of information collected by the Archive show that Cataclysm was sudden and unexpected. It is believed that the etherspace beacon network played a key part in this disaster, supported by a single scrap of data mentioning a surge of ether-energy right before chaos broke loose.
No clear account of what happened, just confusing, half-complete log entries from ancient ships, describing madness and havoc, and even those cease after a certain date. There is only silence for the next thousand years, until the founding of the Empire. Later, folktales and legends on nearly every planet would speak of evil spirits and constructs awakened by a curse, and empty worlds which had their own weapons turned on them dotted Imperial territory. What exactly happened would only be pieced together after the founding of the Empire.
The First Empire
The Old Coalition had left a trove of technology behind, much of it preserved beyond the reach of the monsters awakened by the Cataclysm. However, the knowledge base to expand on that technology was not simply forgotten, but outright lost. There was no way to gain it back.
The Archive learned this when they tried to venture into the massive computer banks underneath Tarsis's surface, only to find that the information had been scattered, corrupted, defiled, and warped to the point of uselessness at best, malevolence at worst. Even with their zaian master, Atheran, and the new Imperial army assisting them, the Chroniclers were only able to retrieve the most basic data on etherspace engines, spaceflight and navigation, and the general sciences of physics and engineering, at great cost.
There were all manner of demons waiting below the surface, none of which were pleased that their nightmarish domain had been trespassed on. Machines built by machines fit only for the slaughter of life were still active, driven to greater insanity by their centuries in the darkness; they blindly attacked anything they came upon. Three more armed expeditions ventured down into the computer banks, only one returned, and what it brought back laid waste to a quarter of the Imperial City the moment it was activated. No more expeditions were sent below Tarsis, and what is down there has been sealed off ever since.
With blood and sweat, the first Emperor unlocked the orbital spires, where he found entire communities who had survived for centuries in the space stations above, who exchanged their services and loyalty in return for permanent residence in their homes. Somehow, one of the station's digital libraries had a few surviving records, among them a priceless file containing the physics and mechanics behind plasma weaponry, and a fragment of instructions regarding etherspace beacons. From there, the Tarsins activated the silent fleets, and began the reconquest. While the means to replace what was lost were no longer available, at least there was still something left.
A Second Fall
The Age of Shadow Emperor and the Salvation of the World caused such widespread destruction and displacement that they have been compared to a second Beacon Cataclysm. What the Old Coalition had left behind and what had fueled the First Empire was reduced greatly, and the knowledge base even more eroded. The Shadow Emperor completed what the Beacon Cataclysm had began; the treasures of the ancient World were scattered and ruined, their power would never return to the Tarsins. Not only was the means to replace what was lost gone, but most of what remained was now gone as well. The heights of power the First Empire reached would never be matched again.
With their return to the affairs of the mortal World, zaian had hoped for a time that they would be able to pick up the pieces, but the pieces that remained tried to kill anyone that touched them, or were so degraded they were beyond useless. They considered giving their own technology out, but there was a two-fold problem: if most zaian were too irresponsible to be trusted with it, how could the Tarsins and others be? This was compounded by the rapid spread of the New Faith, which taught a distrust of technology and a disdain for the material; it was not worth the cost.
This new cultural ideal would not change anything, though, as the Second Empire's quest to restore order to the World turned into a war of defense against everything else. The plague's appearance, the rise of Sarthîon, Aichar, and other barbarians realms, the constant incursions and attacks by aliens unknown, and most of all the Shadow Emperor's reign, all changed the Tarsins into a people focused on driving back all threats at any cost; a viewpoint quickly spread to the young races they drafted into service, like the Digondarians and Arkanin.
The zaian realized what the Tarsins had come to accept long ago: there was no recovery coming. There was no resurgence of the golden age just around the corner. All of that had been smashed, burnt, and broken. Even if the Tarsins had wanted to reach again their old heights, it would now be impossible. The base of technology to build upon is gone, scattered to the four cosmic winds by curse and contagion. The time and resources needed to match millennia of peaceful development simply do not exist, and the mortals of the Coalition scorn that development, as it created what brought them so low in the first place. So the zaian set about a new task, one of inspiring courage and hope among the mortal races, to keep the struggle from ever faltering.