Definitely some take on the necromancer Nybeth from Tactics Ogre: LUCT, whose series had an enormous influence on the Ivalice games and subsequently FFXIV. They outright played his theme song (who in turn shared primary composers, explaining the similarities in sound).

Many others pointed out he also looks like an FF11 Corse, who in turn is loosely based on FF1's Lich. Nybeth in his time in the Palace of the Dead / Hell Gate in TO has him transforming into a Lich himself, where he's fought as a possible final boss the massive super dungeon.

I wouldn't be surprised if they merged aspects of Scarmiglione into him as well, or vice versa, in an attempt to make it more Final Fantasy and natural to XIV instead of outright porting the character.