The Reasoning behind The Sundering? (*6.0 Endwalker Spoilers*)

[Rosenstrauch]

It does not seem likely that old Lahabrea, who did not care much about his son, would somehow care about Elidibus. It is much more likely that Erichtionios, who met Elidibus in Pandaemonium and thus came to care about him, is our Lahabrea.

The problem with that is that, per Emet-Selch, the Lahabrea who was eaten by Thordan was the same Lahabrea who created Phoinix. Erichthonius sucks at using any magic at all, with the only notable exception being the sealing magic used in Pandaemonium.