So I just picked up the Omens of the Pharaoh expansion, and as I was looking through it I realized most of the mask monsters were really old Chaosium-era pulls. Which is fine, but is a little on the dated side. Since I've never seen these all listed anywhere else, I thought I'd post a few more modern avatars that have been cooked up since the old days, just in case FFG wanted a little more gas for a future expansion. Also, potential spoilers for some pretty good videogames, so read at your own risk. If anyone else knows of some oft-overlooked Masks, post them here as well!

(Specifically Darkest Dungeon, Witcher 3, and Persona 2)

The Walkin' Dude, Randall Flag (Stephen King's "The Stand" and others)

Gaunter O' Dimm, Master of Mirrors / The Man of Glass (Witcher 3, Heart of Stone DLC)

Great Father (Persona 2: Innocent Sin)

Heart of Darkness (Darkest Dungeon)

On 9/19/2018 at 10:00 PM, Sinthioth said:

Gaunter O' Dimm, Master of Mirrors / The Man of Glass (Witcher 3, Heart of Stone DLC)

As far as I know this one is inspired by Randall Flagg and some other characters and myths.
You could decide that he's a Nyarlathotep mask in your own content, but saying that he's a mask in the Witcher is quite a stretch.

On 9/19/2018 at 10:00 PM, Sinthioth said:

Heart of Darkness (Darkest Dungeon)

I would call that an even bigger stretch. Why do you think it's Nyarlathotep and not another, existing or new, entity?
I'm not saying it certainly isn't. I'm saying I haven't seen any evidence that would support such notion.