In Aztec mythology, Mictlantecuhtli was the skeletal god of death who ruled over Mictlan, the underworld, with his wife, Mictlancihuatl.
After the restoration of the sky and earth by Tezcatlipoca and Quetzalcoatl, the two gods decide to create people to inhabit the new world. In order to do this, Quetzalcoatl travels to the underworld to retrieve the human bones of the last creation. After a conversation with Michlantechutli, the Lord of Mictlan agrees to give up the bones if Quetzalcoatl will complete a task that involved Quetzalcoatl traveling around the underworld four times while sounding a trumpet made out of a conch shell. Michlantechutli, however, not wanting to give up the bones so easily, makes the apparently simple task challenging by not drilling holes in the conch shell. Quetzalcoatl, nevertheless, is able to complete the task by calling upon worms to drill holes in the shell and by having bees enter the trumpet.
When Michlantechutli hears the conch sounding, he at first allows Quetzalcoatl to take the bones, then quickly changes his mind, but his efforts are in vain as Quetzalcoatl is able to escape the underworld with the bones. Angry at the fiasco, Michlantechutli orders his minions to dig a deep pit, and as Quetzalcoatl runs towards it, a quail pops out and frightens him. Quetzalcoatl falls in the pit dead, and the bones are broken and scattered – the reason why people are different sizes today.
Quetzalcoatl eventually revives and retrieves the bones, and gives them to the goddess Cihuacoatl (Woman Serpent) who grinds the bones into a flour-like mixture and puts it into a special container. The gods are then able to gather around this container, shed drops of their own blood, & from the combination, spawn the peoples of today.
Nature of Spirits in the Goetia