structural:reformatting, quality:corruption
Cosmology and ritual

The Aztec world consisted of three main parts: the earth world on which humans lived (including Tamoanchan, the mythical origin of human beings), an underworld which belonged to the dead (called Mictlan, "place of death"), and the upper plane in the sky. The earth and the underworld were both open for humans to enter, whereas the upper plane in the sky was impenetrable to humans. Existence was envisioned as straddling the two worlds in a cycle of birth, life, death and rebirth. Thus as the sun was believed to dwell in the underworld at night to rise reborn in the morning and maize kernels were interred to later sprout anew, the human and divine existence was also envisioned as being cyclical. The upper and nether worlds were both thought to be layered. Mictlan had nine layers which were inhabited by different deities and mythical beings. The sky had thirteen layers, the highest of which was called Omeyocan ("place of duality") and served as the residence of the progenitor dual god Ometeotl. The lowest layer is said to have housed the fire god and was level with the Earth.

After death, the soul of the Aztec went to one of three places: the sun, Mictlan, or Tlalocan. Souls of fallen warriors and women that died in childbirth would transform into hummingbirds that followed the sun on its journey through the sky. Souls of people who died from less glorious causes would go to Mictlan. Those who drowned would go to Tlalocan.

In Aztec cosmology, as in Mesoamerica in general, geographical features such as caves and mountains held symbolic value as places of crossing between the upper and nether worlds. The cardinal directions were symbolically connected to the religious layout of the world as well; each direction was associated with specific colors and gods.

To the Aztecs, death was instrumental in the perpetuation of creation, and gods and humans alike had the responsibility of sacrificing themselves in order to allow life to continue. This worldview is best described in the myth of the five suns recorded in the Codex Chimalpopoca, which recounts how Quetzalcoatl stole the bones of the previous generation in the underworld and how later the gods created four successive worlds or "suns" for their subjects to live in, all of which were destroyed. Then, by an act of self-sacrifice, one of the gods, Nanahuatzin ("the pimpled one"), caused a fifth and final sun to rise where the first humans, made out of maize dough, could live thanks to his sacrifice. Humans were responsible for the sun's continued revival. Blood sacrifice in various forms were conducted. Both humans and animals were sacrificed, depending on the god to be placated and the ceremony being conducted, and priests of some gods were sometimes required to provide their own blood through self-mutilation.

Sacrificial rituals among the Aztecs, and in Mesoamerica in general, must be seen in the context of religious cosmology: sacrifice and death was necessary for the continued existence of the world. Likewise, each part of life had one or more deities associated with it and these had to be paid their dues in order to achieve success. Gods were paid with sacrificial offerings of food, flowers, effigies, and quail. But the larger the effort required of the god, the greater the sacrifice had to be. Blood fed the gods and kept the sun from falling. For some of the most important rites, a priest would offer his own blood by cutting his ears, arms, tongue, thighs, chest, genitals, or offer a human life or a god's life. The people who were sacrificed came from many segments of society and might have been a war captive, slave, or a member of Aztec society; the sacrifice might also have been man or woman, adult or child, or noble or commoner.