My speculation is this is linked to Azem. We've seen evidence that the scripts used by the Ancients is in Solution 9. We also have the purposeful plot hole about what Azem was doing during the final days. We also know from Shadowbringers that Amourot had a sister city. The title Dawntrail references the sun, which we know is the symbol of Azem. Azem wasn't born in Amourot because they were discovered by Venat during her adventures outside of Amourot. And frankly, Azem not returning to Amourot for the summoning of Zodiark and Hydaelyn, which really was a civil war between their former teacher/advisor and their closest friend, implies that Azem was doing something much more important than the sundering.

And don't forget the cryptic message from New Years, speaking of the expansion as question if it's a new adventure or a homecoming. In a literal sense it's a new adventure for the players/Scions and homecoming for new Hrothgar woman. But it could also be a metaphor the WOL's new adventure which is also a homecoming for Azem.