Draeris

Lorewise it should have been in existence since Aegis as three of the four descendant races found their way to it in tribal form while it was not discovered until Anthos/Asulon something like that.

Even if it is canon, it would have only been reachable during the Asulon/Anthos era because of the portal to the Verge. Taking a portal from Anthos into the Fringe establishes that we are now once again in the Aegian realm - thus Aeldin is once again inaccessible, unless you get a portal back to the Verge/Asulon/Anthos

The Verge wasn't in another world though, at the time I recall it being explained that we were port'd to another point of the world that was safe rather than a separate world. And the transition between Anthos and the Fringe was some stupid underground tunnel, what I believe you are referring to is Fringe to Thales in which we all just woke up in Thales.