As much as I try to keep from speculating about future matters these days, it could stand to be mentioned that the object of the song, if primal-related, need not be about the demigods themselves. Throwing on the ol' darksteelfoil hat, it could just as easily be about the tribes that worship them, as if the song were a warning from "those who walked before" to "those who walk after" that if you go about this whole Era / Ascian / Calamity / Hydaelyn / Zodiark thing in the wrong way, that your soul will be torn and your body forsaken. An origin story for our enemies, perhaps.