Final Boss of "The Twinning" Hunting for lore (Spoilers)

[Iscah]

It's Nero Scaeva (remember him?), from the end of the CT raid series when he throws his aether detector into the Syrcus Trench (which, I believe you retrieve later in the 5.0 sidequest "You Had One Jobb").

I tried to get a good picture of it but it is at a strange angle.

Still, I'd recognize that guy, that cutscene, and that hobo trenchcoat anywhere.

Thanks for the correction - I did realise it on a closer look when I was going through screenshots the other night, and have been meaning to come back to fix it.

And yes. It's a bit hard to forget him.

Not sure about the quest though (script here).

UNGAINLY GUARDSMAN
What exactly are the contents, you ask? Among other things, there happens to be a remarkable device that's been entrusted to us in the guard by the Crystal Exarch himself, who is said to have exhumed it from the Crystal Tower!
Though it simply looks like a pretty round gemstone, it somehow has the ability to measure the concentration of aether in the air and matter around us. Needless to say, it's not something that anyone─not even the artisans at the Mean─can just toss together. If I had lost it for good...

I'm not sure if the physical description of "a pretty round gemstone" fits - and we know from the ending, and can assume from his general inability to move far from the tower, that G'raha Tia can't travel to the Source through the portal. So how then could he "exhume it from the tower" or otherwise acquire it - or what else might it be? It could be a hook for something important, or is it just another "the Exarch has access to mysterious artifacts" thing for world building...?

Something to ponder.

(Of course he did get the other beacon device into the trench somehow, but I can only assume he tossed it through the portal.)

...

...what it does make me think of is Koh Rabntah/Noah.

SYELE
I am sorry to trouble you so soon after your trials in the Crystal Tower, but my colleague Koh Rabntah has gone missing.
She discovered the oddest orb deep within the tower, and said she was returning here to analyze it.

KOH RABNTAH
You are speaking with none other than Noah, archmagus of Allag! My scholarly works are legend, my treatises of the cosmos priceless, and my very name known throughout the world!
...Or 'twas so once. My soul has whiled away the millennia within an orb. Koh awoke me from my slumber, and... Well, how could I pass up a chance to walk the world again? So I allowed my spirit to flow into her body, and here we are.

And having just redone the first part of the Ridorana unlock quest... hmm.

MIKOTO
Simpler... Right... Um... Aether is not only the building block of all things material, but those immaterial as well. Thoughts, memories, feelings, one's very will are all understood to be aetherial phenomena, and can be measured as such. Unlike most crystals, which only can emit elemental energies, auracite is tuned not only to absorb aether, but aether specific to the immaterial. That aether is then stored and multiplied within its crystalline confines until external stimuli precipitate release.

CID
Try again.

MIKOTO
Uh... Ahem. Under appropriate conditions, a strong will or desire can become imprinted upon the auracite and stored until fomentation, at which time the desire becomes manifest─

RAMZA
Fomen...tation?

CID
What my studious young friend is trying to say is that the Otius takes one's deepest fantasies and makes them reality.

The final conclusion doesn't quite match, but middle of the description certainly does - and I have a sudden suspicion as to what Noah's "oneiromantic pearls" might be made from...