A very religious people, they built many temples to their gods, whom they believed needed constant human sacrifice to be appeased. (TV: The Aztecs) Their most notable god was Huitzilopochtli, the god of war and the sun, to whom human sacrifices were made in which the priest cut out the victim's heart. (PROSE: A History of Humankind)
They had a myth known as the Five Suns in the Sky. The five said suns were Four Tiger, the Sun of Air, the Sun of Fire and Rain, the Sun of Water, and the Sun of Man. They also believed that there were thirteen heavens. (TV: The Aztecs)
The Aztecs were extremely warlike. (TV: The Aztecs) They often fought 'no-killing' wars in which opposing armies would take as many prisoners as possible, and the war ended when each side had enough prisoners to sacrifice. (PROSE: A History of Humankind)
The Aztecs had a concept of retirement: "all who attain their fifty-second year shall pleasurably pass the remainder of their lives free from responsibility and care." They then lived in the Garden of Peace, and were often consulted for their wisdom.
They treated their women poorly. The Code of the Good Housewife stated, "Tend well your nurseries and your flowerbeds. Keep clean your pot and stew pans. Do not spend recklessly. Do not destroy or cheapen yourself." If these commandments were not followed, they were not given houses.
Women were given prearranged husbands, and had no say in the matter. It was a custom for an Aztec man to present a cup of cocoa to a woman whom he wanted to marry. The woman, however, must look down upon meeting him, and not look into his eyes. (TV: The Aztecs)
When the First Doctor and his companions encountered Aztecs in the 15th century, the Aztecs perceived Barbara Wright to be a reincarnation of the priest and god Yetaxa. Despite the Doctor's pleas that time cannot be rewritten, Barbara attempted to persuade the Aztecs that the gods did not require human sacrifice. This, however, led to Tlotoxl accusing her of being a false goddess. Meanwhile, the Doctor offered Cameca cocoa, unknowingly proposing to her. Eventually, Barbara was proved to be false, and they managed to escape into the tomb in which the TARDIS was trapped. (TV: The Aztecs)
Barbara later thought often on her failed attempt to change history with the Aztecs. She mentioned it while in Paris in July 1794 during the French Revolution (TV: The Reign of Terror) and in Salem Village. (PROSE: The Witch Hunters) Shortly they left Mexico, the Doctor asked her if she was still thinking about it. (TV: The Sensorites) Ian reminded her of it while at Masada (PROSE: The Last Days) and after they departed the Mary Celeste; (PROSE: The Chase) the Doctor also reminded her of it. (PROSE: The Witch Hunters)
After leaving the Doctor, Barbara became a university lecturer on history, specialising in the Aztec period. (PROSE: Who Killed Kennedy) Her dissertation was on the fall of the Aztecs. (PROSE: Nothing at the End of the Lane)
The Fourth Doctor recalled the Aztecs as one of the civilisations which had created twisting underground passageways which he had to run up and down. (PROSE: A Device of Death) He later claimed that the dinosaurs' blood rituals rivalled those of the Aztecs. (PROSE: The Dragons of Prague)