Thanks to ginja_ninja for the inspiration!
So according to the Final Fantasy Wikia:
The Occuria are the most powerful beings in the world of Ivalice in Final Fantasy XII. They are referred to, by themselves and others, as “The Undying”, though their existence is unknown to Ivalice at large. The Sage Knowledge available via the bestiary suggests the Occuria used to live on Ivalice among the other races before withdrawing into their own realm. The Occuria live high above the Giruvegan, higher than any airship can reach. The way there is in the bottom of the Great Crystal.
But take a look at Venat’s design.
As for the black mage in Final Fantasy history:
Their faces are not visible in the shade of their hats, except for their eyes which shine brightly. A Black Mage’s primary ability is to cast Black Magic, which usually consists of attack spells, but also contains some effect spells.
And each of the Occuria has these have these same characteristics.
One theory: black mages became black wizards, then “ascended masters” able to transcend time and space…