This mask is a depiction of the Aztec god Tezcatlipoca; tqhis god was also known as the Smoking Mirror. Of the variety of masks to select one from, this mask had the most unique construction; the face structure is layered on a real human skull. Alternating blue turquoise and black lignite mosaic strips cover the skeleton, furthering the "smoking mirror" appearance. The teeth appear to be real human bone, and the nasal cavity and orbits were made using sea creature shells (from outermost regions of the empire). At the rear of the skull, bone is chipped away and covered with deer skin to allow a priest or authority figure to actually wear the mask over his face.
I find this mask frightening. Though I do not know much about Tezcatlipoca specifically, Aztec gods have an intense reputation. Many aspects of their character hinge on consequences. The mysterious nature of this god's face mask seems intimidating, as if after creating the world on a whim, he may demolish it at any moment. By using a human skull, humanity has been creepily integrated with the god person, maintaining the same structure and form, but escalating the perceived power capabilities. I find it menacing that this "creator" god is so evil in appearance. I would hope that a creator was loving and valued his creation, not appearing as if he was waiting to punish it.
For more information on this mask, check out The British Museum's website: http://www.britishmuseum.org/explore/highlights/highlight_objects/aoa/m/mosaic_mask_of_tezcatlipoca.aspx
