Nahua religion held that the present world is the fifth, that the four before it ended, and that this one moves only because the gods gave themselves at Teotihuacan to set the sun going. Human offering is repayment on that debt, and the Mexica state organised it at a scale the Spanish found both appalling and useful to report.
The pantheon is layered. A dual creative principle, often named Ometeotl, stands behind everything and receives no cult. Below it Tezcatlipoca, the smoking mirror, is the arbitrary power of fate; Quetzalcoatl the feathered serpent is associated with wind, with priesthood and with the recovery of the bones of an earlier humanity; Huitzilopochtli is the Mexica tribal god who led them to Tenochtitlan; and Tlaloc, far older than any of them, holds rain and the mountains. Eduardo Matos Moctezuma's excavation of the Templo Mayor found Huitzilopochtli and Tlaloc sharing one pyramid with two shrines, which is the clearest statement of what the Mexica understood themselves to be doing.
Elizabeth Boone's work on the divinatory books shows how time was read. The 260 day count assigned each day a number, a sign and a patron, and the specialist consulted it for naming, for marriage, for travel and for war.