This suggestion has come up a few times, along with some mentions of Alexander's potential relevance (as it is important in FFIX?) and that swirled up a relevant quote in my mind: Mide was given the summoning horn by Travanchet along with an instruction to wish for her heart's desire.
Having dug up the full actual quote, it seems even more potentially relevant - from
The Coeurl and the Colossus:
The horn itself is accounted for, of course - it's currently embedded in Alexander's core - but it sets me wondering if they're trying to connect back up to this plot thread, and what other similar relics might be out there.
The Enigma Codex itself was an odd thing, alien-looking technology at the time of that story, but now with further developments it could possibly be electrope or something like it. We never got a really clear full picture of its history either, IIRC, and I've forgotten what there was because it always felt like a fairly minor detail at the time.