On The Evolution of the modern day Elezen

[Vaerimont]

Where this fits into wider Eorzean history with the history of the elezen is that earlier in the game, Gridania was stated as having been founded 'some 500 years previously' (the game is a little vague on the exact amount of time in the past it was) when the moogles interceded on the inhabitants of Gelmorra's behalf to settle in the Black Shroud, uniting with the newly arrived Midlander hyur.

This is new to me! I had known and assumed that some amount of moogles had retreated from Sohm Al along with the Elezen which was so eloquently evidenced by the fairy tale of Good King Moggle Mog XII; being that once the 'gods' those moogles has served began warring, King Mog XII held a long rope so that his subjects might descend to land below, but I was unaware that it was these same moogles themselves that brought about the treaty between man and elemental.

Exactly when Gelmorra was founded though is anyone's guess - it's possible it might have been sometime after the 6th Umbral Calamity, or possibly even earlier, not (forgetting that the 6th Astral Era ran for 1572 years to the most recent Calamity)

I'm inclined to believe that Gelmorra was founded after the migration of the Hyur into Eorzea as some of the Gelmorran ruins, such as the Tam-Tara Deepcroft, have symbols of the Twin Adder etched into their architecture at certain points. The standard representing the unity between Elezen and Hyur, respectively.