|A skeletal Canine|
|Divine Rank||Greater God|
|Portfolio||Death, Murder, The Underworld|
|Domains||3E: Destruction, Law, Death
The rich history of Dungeons and Dragons is chock full of appropriated culture. From the obvious authors (Tolkien, Lovecraft, Vance) to real world cultural-cliches (Ancient Egypt, Vikings, the Catholic Church), D&D has always lifted its inspirations shamelessly and with various degrees of author understanding. This is good; whilst a nuanced exploration of European mercantile culture in the C14th might be fun for the committed autist, D&D is a game system designed for fighting orcs.
In the real world, Mictlāntēcutli was the primary Aztec god of death and the underworld. His worship involved ritual cannibalism and human sacrifice. He is depicted as a skull faced man, arms spread and ready to tear the dead asunder, and with his mouth agape and ready to consume the stars. Life sized statues of Mictlāntēcutli stood outside the House of Eagles, the temple of the socially elite warrior class, and he was associated with fertility and the dawn. He is prime campaign fodder.
OG DM Gary Gygax 'lifted' Mictlāntēcutli (and other Mayan gods) for the 1979 adventure C1: The Hidden Shrine of Tamoachan as part of the Olman Culture of Greyhawk, turning him into a generic Lawful Evil murder god in the process. His realm is presented in bas relief, featuring scenes such as devils forcing souls to roll boulders up hills, stygian rivers, and people being boiled in pits of lava.
The entire Olman culture was then *immediately* abandoned for the next 20 years, and was barely referenced in official publications until the release of the Scarlet Brotherhood splatbook in 1999. Third edition D&D made Greyhawk the official setting, and Mictlāntēcutli was promoted to greater deity status. His symbol was now a skeletal dog, his priests do human sacrifices. He doesn't even get a mention in the 5e PHB deities of Greyhawk list.
Cultural shorthand is a really convenient way to say things to your players without having to say anything. You know what pyramids and mummies mean. Church spires and inquisitors? bet there are nuns. Longboats and horned helms? Do they have axes and a runic script?
Mictlantecuhtli is a generic aztec death god, cursed with being less interesting than the alternatives; If you're going to include him in your cosmology, embrace the Quetzalcoatls, stepped pyramids, and open heart surgery with flint knives. And remember, The Hidden Shrine of Tamoachan is a really good adventure.