So yeah, FFIV.
IV has the Four Archfiends, Scarmiglione for O5S, Cagnazzo for O6S, Barbariccia for O7S and Rubicante (the leader of 'em) for O8S.
And if you played the 3D remake of IV, you know there's an optional boss called Geryon which is LITERALLY all four fiends combined into a monstrosity. A
sum of them all?
Sigma(
Σ)?
So in O8S phase 2, they all fuse into Geryon?
Also Sigma is the 18th letter in the greek alphabet, and Geryon appears in the Canto 18 (CANTO XVIII) of Dante's Divine Comedy: Inferno.
The thing that bothers me is that
they said the new armor set will be the "Diamond" series, and although FFIV has Diamond Armor, the last boss in FFII actually drops the Diamond Armor, so who knows.
PS: I'm kidding, I know nothing in here is definitive proof, please. But it makes cents.