Had an idea watching an episode of Bleach.

The face masks worn have demonic visages on them, but because they are fixed and cannot change their expressions, the initial fear inspired by them gives way to familiarity.

Then in my mind's eye I saw a perfectly blank mask, hemispherical, covering the front half of a shinigami's face. Same white material used for the hollow masks.

Then two horizontal slits slowly form, and the mask slowly changes in delayed response to his surroundings, or external stimuli. Grotesquely deformed maw of teeth, dementedly laughing face. The fear will arise from the over-reaction from the mask, or the impropriety of the mask to the given circumstances, and off-course will reflect the fact that the emotions of the wearer are ever shifting, and that the viewer is totally incapable of pinning his finger as to what these emotions are.

V for Vendetta only worked because of Hugo Weaving.

In 300, when they placed the masks on the "Persian Immortals", or in Japanese Noh, when the place a mask on a senryuu, the idea is to fix one expression on it, so that the person becomes the embodiment of that emotion or response.

A blank, ever-shifting mask will be most alien to a viewer.