Last dungeon.

[Comguitoz]

Anyone knows which mob drops the Hierophant White Mask in the last dungeon? Missing one of these items to get the achievement.

[starry113]

You've probably either figured it out or just gone on since now but for anyone else wondering, Voidblack ♥♥♥♥ Pento drops these. They're the ones that look like a pair of legs hopping about in one shoe with a purplish hat on.

[Blunette]

Pretty sure you can also buy masks from vendors on Virga Island or the Eugief Vendor in Brilehaven. I don't remember which one sells which, but one of them sells the Arcana masks per day and one of them sells Demon masks.