I wonder why seemingly none of the unsundered ever went to Hydaelin to have a talk? If we could find her in the aethereal sea as lowly sundered fragments, it should be no problem for them to reach (especially emet - hades, keeper of the underworld or how it was called).

They know that hydaelin isn't just some god or mindless primal, that she has an ascian as her core same as elidibus is for zodiark. Someone they possibly even knew or were friends with (emet and vemat seemingly had quite some familiarity with each other). In all the time since the sundering they never thought to go talk to her, hear her reasons? Or at least clarification on the more precise circumstances of the sundering? To seek a dialogue with the 4th unsundered ascian / ancient, Venat.