I noticed this on the discord and wanted to save it here because it is a valuable Q&A:
Alila, game channel wrote:Is there a date when the first undying...not dying was recorded, at least approximately? Was it only after the fall of Aetgard, or was it a phenomenon even during it?
Rias wrote:The Undying condition has only been verifiably observed in the Lost Lands region. There were rumors of similar occurrences before Aetgard's fall, but then there were rumors of a lot of things. The general consensus outside the Lost Lands is that the whole Undying thing is myth and folk legend, or an exaggeration, or just evidence of those Exiles having gone mad. It's only really accepted by people who end up in the Lost Lands themselves and observe it for themselves. The Lost Lands general thinking is that it does seem to be happening an awful lot, and there's a lot of speculation as to why that is and whether something related to or just timed closely to Aetgard's fall has anything to do with it.