Pretty sure the extent of what we know is from Emet-Selch's recounting of the Final Days of Amaurot in the eponymous dungeon from back in 5.0. Though admittedly my interest in the story has largely waned, so I could've missed some mention in Anamnesis Anyder or forgotten details and such. Sound came from the earth, Ancients' creation magicks started going haywire and giving birth to their fears and nightmares, rocks fall and most everyone dies. In so far as I am aware, they've yet to elaborate in any way on what the sound is supposed to be, with the only possible source of potential information off the top of my head being the Scions' trip to Anamnesis Anyder since the MSQ has largely been more concerned with getting the Scions back to the Source than anything. I seem to recall mention that the calamity which befell the Ancients started on the "mainland" and took some time before it reached Amaurot. Long enough that rumours of what was happening abounded and they'd (the folks at Akadaemia Anyder) gathered specimens to research.