The rift, the crystal tower, and the seat of sacrifice (Spoilers up to 6.0)

[Nav_Fae]

It's mentioned that the same cry was heard in the present day before the incident in Thavnair, so whatever the source of it was is still around.

I'm really hoping it's not just a red herring and that it has major significance.

I always thought the cry was Meteion
Like signaling the start of an attack.
After you defeat Zodiark on the moon, you get an echo vision where the planet turns black and Meteion says, "Ah, At last." very sinisterly. I always thought the cry was her for some reason.