Fall of the Neatherese

Documents detailing the fall of the Neatherese Civilization are scarce, which itself is telling as the various subsections of Neatherese society documented even the most banal of things. Those works that have been recovered indicate that the fall was not caused by a single disaster, or at least the civilization persisted in the aftermath of said event. There are refences to a "choice," "mistake," or "folly" that appears to have begun a complete collapse over the next century of the greatest civilization on the face of Sanzeia.
Neatherese writings, contained in magical stonework -- which some believe contains troves of information that the modern world has lost the ability to access -- are heavy in references to other things that assumedly would have been obvious to a person during the Age of Myth but have been since lost. Still some common themes related to the fall have been identified:

• A choice was made that impacted all of Neatherese society
• That choice turned the gods against the people. Of note, there is a marked shift in this period from contempt to hostility to reverence to faith where divine beings are concerned.  This aligns with the common interpretation that the civilization itself was being punished by the the Thirteen for its transgressions.
• There can be a general sense inferred from the texts that the Neatherese fell an end was coming slowly and inevitably.  Texts almost seem to use the fall of various states as a method of keeping date.
• There are numerous efforts to attempt to magically advert, or more likely survive, the cataclysm. Over time a desperation and madness seems to set in at the upper levels of Neatherese society and while most of the details of these proposed means of "escape" or "adaptation" are lost, a distinct coldness and callousness creeps into the sources over time.
• The fall ultimately seems to have been complete when the last few of the Neatherese castles "were lost."  Older texts refer to castles "falling from the sky" and some scholars have placed a great deal of importance on the difference in terminology.  Regardless of the actual event, it appears that a significant portion lower and middle classes survived the fall (some scholars argue that these were people left behind) and while cut off from Neatherese technology they returned to the old ways and land of Sanzeia.
• Given the age of cities founded across the Elowean Plateau it is generally assumed that the survivors of Neatheril descendants were the original founders of much of the human kingdoms. 
• Culturally, it appears that a distinct effort was made to erased the Neatherese civilization, thus no hero of the age of myth refers to themselves as being "of Neatheril" though some may have wielded weapons or magics left over as relics.