Age of Chaos

This is mentioned just once, at the start of the Background info:
Then came the Age of Chaos. And the Elves, to the last one, fled South
So the implication is that this was something that 'happened' to the Elves and the land, rather than something they intended - and their fleeing North Island was their response to it. So what happened???
And the corollary - why have they now decided to return?
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From Legend 23 - Temple of the Dead:
"least you offend Her Divine choosing and bring damnation and curses upon our path as was done at the start of the Age of Chaos by her anger"
This legend must therefore postdate the GSOV, but also implies that some calamity hit the Undead after the Elves left - so we could posit that this calamity was what the Elves were running away from - or alternatively - could have been caused by the Elves' GSOV/Spell of forgetting.
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Q: How long ago were the elves originally around on the North Island?
DP: The general guess is around 300 years ago
Q: What was the period of the Age of Chaos?
DP: From the leaving of the Elves for about 100 yearsEmail2020-07-07 19:58
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The Legend of Sorleaf refers to the Twilight of Change: Was this a symptom of the coming of the Age of Chaos, or its cause?
'Just before the Twilight of Change when the days of Chaos came quickly upon the world, there was a half formed Elf called Sorleaf. What manner of disruption spawned his birthright is not recorded but it was astounding in its time. Little did they know that his misfortune was but a precursor of the horrors to follow the Twilight.'
Could this have been due or related to the Gods of Saratan?
Or a wild idea - without any basis whatsoever: Could the magic/mana of North Island have somehow failed/become unusable causing them leave - and perhaps this is what caused the grounding of the remaining Flying Cities.