About the dark crystal true identity [Spoiler T13]
I don't think I saw any discussion about this recently so tell me if someone already noticed this:
So until now there was multiples theories about who is the dark crystal we see at the end of the 2.0 story quest, either Zodiark, Hydaelyn weakened, or a dark Father crystal.
But then I finally reached T13 and that's when I saw this below the platforms of the battle arena :
Yup the Dark Crystal seems to be Bahamut Prime. Which was kinda obvious in a way, we have this vision right before Bahamut roars as if Hydaelyn reminded us that the big bad dragon was still alive. The resemblance to Hydaelyn might simply be explained by the lack of time at release to design a unique crystal for Bahamut.
Simply this is the true form of Bahamut, just like Atomos prime, it's the crystalised ether in which then takes the form of bahamut to defend itself.
I wonder also if the arena isn't simply some kind of mirror, the bottom part is the crystalised ether of bahamut and the upper part is the manifestation of his will, but I may be over thinking it.