The Aztec civilisation believed that the sun fought the darkness each night and in rising it would save mankind. In its rising, they believed that the only way to make the sun rise was to feed it blood, however, it has never been clarified if it is animal or human blood that keeps the sun rising.
They believed that the earth was flat and in the realms of heaven and hell, there were 13 heavens and 9 hells.
In the aspects of religious offerings, the Aztecs believed in cult worship. They would worship at temples called the Teocalli which was outfitted with sacred pools (for the ceremonial cleansing), gardens, living quarters for the priests, and the most interesting of all…shelves were equipped in these temples to hold the skulls of the victims.
Sacrificial ceremonies played an important role in Aztec civilisation. Sacrifices were usually made to appease the sun god, not only were people in the village sacrificed, but prisoners from battles were used to sacrifice to the sun god. Now, the human sacrifices were not only for the sun god, but offerings for the sun and the earth so that food would grow.
There is an exceptionally strong emphasis on the afterlife in Aztec religious beliefs. Unlike many of the other Mesoamerican and Mesopotamian beliefs, the Aztecs believed that it was not how you lived that determined if you went to the sun god or to the underworld when you died, but rather the way in which you died.
Now, the rules to the afterlife are this: If a person dies in the normal way, their soul must first pass through the nine lives of the underworld before reaching Mictlan (the realm of the dead). However, a woman who died in childbirth or a warrior would ascend straight to the sun god in the sky.