Hazardous Material

Question: Many months ago I asked about Xipe Totec being the odd man out in the Teotl, that he was the only member of the pantheon not family to any of the others; but the death god, Mich-can't spell the rest, is ALSO unrelated to the rest of the pantheon. Does the gods of death being separate from the other gods have some special cosmic significance to the Aztecs, or is he unrelated to the rest of the pantheon for a different reason, like it shows that the other gods just don't like him or hes different?

Mictlantecuhtli is the guy you're looking for. If it would help to break it down, the word "Mictlan" means literally "place of death" and is the underworld (from mict-, to die, and -lan, a place suffix), and "Tecuhtli" means literally "lord" or "noble" (from tec-, a stem used for words such as "grandfather" indicating respect). So his name is really just literally "Lord of the Underworld", which makes sense because being boss of Mictlan is what he's all about.

But it is still a handful to spell for non-Nahuatl-speakers, so don't sweat it too much. It'll come with practice!

Mictlantecuhtli is definitely treated somewhat differently in Aztec mythology, you're right; he has a few myths, but generally even in those he is the figure someone else comes to or interacts with, and seldom goes out to do so on his own for any reason. He spends the entirety of his time in Mictlan, lording over the dead in their silent hall with his similarly depressing wife, and does not go on adventures with his people like Huitzilopochtli, get involved in other gods' business like Tezcatlipoca or make sweeping changes to the Aztec cosmology like Tlaloc or Chalchiuhtlicue.

The reason for this is actually far-reaching across a lot of Mesoamerican civilizations, not just the Aztecs: Mictlantecuhtli is about death, and death has a special place in both the cosmology and outlook of many ancient Mesoamerican cultures. Death, as a general concept, was an idea of especial fear and loathing, containing all the terrible ideas of fear, decay and opposition to life itself, which should not be surprising for a culture that believed that the divine power for anyone to do anything was contained in their living blood and therefore lost irrevocably upon death. This is why death gods among the Aztecs (and the Maya, who are even more violently opposed to it and therefore fear the massive terror of an entire realm dedicated to it, Xibalba) are almost always extremely horrifying to look at and be around. Skeletons, rotting flesh, scary teeth and so on are visual markers that clue us in that death gods are not only associated with the hereafter, but also that that is a terrible and distressing place, one that the living should avoid at all costs for as long as possible.

Mictlantecuhtli isn't related to the other gods primarily because he is Of Death, and the other gods are Of Life; the two things don't go together, and when they interact it's usually with disgusting or tragic consequences, such as Quetzalcoatl almost dying in the attempt to retrieve the bones of humanity from the underworld or Xochiquetzal being injured and disfigured by the bat stealing parts of her very body to deliver to the dead king. This is probably also why he needed to have a wife essentially made for him rather than chosen from among the other gods, none of whom would be in any way up for that kind of horror becoming their everyday existence. The worlds of the living and the dead are not supposed to interact in Aztec myth, and that means that despite his obvious existence and importance, Mictlantecuhtli himself doesn't interact with the other gods much, either. He's not supposed to; he's supposed to stay in the underworld and handle all the dead stuff so everyone else doesn't have to.

This doesn't mean that Mictlantecuhtli is necessarily bad or evil. On the contrary, he performs a vital function: keeping the underworld separate and inviolate, so that the dead can never escape from it and threaten the world of the living. He is in a sense the defender of humanity, in that without his stewardship it is possible that the horrifying creatures of the great below would leak out and threaten all life on earth. Like many death gods in cultures that have a healthy fear of the dead, he has to exist in order to make sure that life is separated from death and thus protected. It's a dirty job, but someone has to do it (and summarily be deeply, deeply disliked and avoided by everyone else).

He's still terrifying, however, and horrible, and no one living wants to be around him, and everyone is generally hoping to die in some way that doesn't involve ending up in Mictlan with him if at all possible. But, to paraphrase what someone else once said... sometimes it's better to reign in the underworld than to be a nobody among the other gods.