A quick look at: Mictlantecuhtli, the Aztec god of death and lord of the underworld.
Mictlantecuhtli was believed to live in Mictlan, the cold, damp and gloomy underworld of the Aztecs, or lower part of the cosmos, where the remains of humans were kept.
This Templo Mayor Museum figure of Mictlantecuhtli, which is perhaps one of the most famous representations of the god, was found in the House of Eagles. Here he wears a loincloth, and stands grinning. Some have suggested that this grin of Mictlantecuhtli, who once harassed Quetzalcoatl on his journey to the underworld, may suggest his desire to torment. His claw-like hands are posed, as though ready to attack someone.
The holes on his scalp would have once been filled with black, wavy hair -which the Aztecs associated with chaos. Parts of his flesh has been teared off, and his liver falls from his chest cavity. This organ was connected to Mictlan, and housed the Ihiyotl soul (see Aguilar-Moreno 2007, chapter 7). Recent residue analysis has found traces of human blood on the statue.
Artefact courtesy of the Museum of the Templo Mayor, Mexico City. Photos taken by Travis: oosik.
Recommended reading: Handbook to Life in the Aztec World (Oxford University Press, 2007) by Manuel Aguilar-Moreno. This is a very good overview and introduction to the Aztec culture, and expands on many of the points I briefly mentioned here.