In regards to Lahabrea coming back to menace us once again -

Bear in mind that he was one of the few Ascians we did not personally kill. Rather his physical form was annihilated and his aether absorbed into the Eye of Nidhogg to fuel King Thordan, then used as fuel sources for Shinryu. While it's... highly implausible Lahabrea's soul could have survived all that, it's not impossible... and gods only know what exactly is going on with Pandemonium in XIV, since all we know so far is that Lahabrea is going to show up there (and that it uses the same architecture as the Void Ark, maybe).

Further, as a roundabout reference to II (Lahabrea the Abyssal Celebrant is the Scion of Light counterpart to Mateus, the Corrupt in Ivalician mythos, who is a reference to Emperor Mateus Palamecia of II, who famously comes back from Hell as the Dark Emperor after being killed and drags Pandemonium up with him) it does make a bit of meta sense to have Lahabrea show up there.

What I find curious is how he's only got half of his Ascian glyph.