Quote Originally Posted by Kaiser-Ace View Post
It very much seems The Mhachi were the enigmatic third faction of The War of the Magi.

And after so much mystery and silence in regards to them as the possible "Proto-Beladians" that have been discussed for so long leads me to believe we may be uncovering the truth about that war and it's consequences too.

It seems Nym was brought down by the, now called, Toneberry Plague which was brought to their city by Mhachi spies. And we know Diablos, The "King Amongst Voidsent", was unleashed on Amdapor by it's enemies. So since they had spies and favored Garlean Style infiltration, I'd say it's likely they are responsible for unleashing Diablos on the Amdapori as well.
It seems highly likely that they were the third faction, though I'm not certain they were the Proto-Bela'dians. Surito Carito mentions that Bela'dia may have been the Mhachi's inherritors to void magic, but he doesn't mention or speculate them being related outside of that.