Quetzalcōātl (often translated as the Plumed Serpent) is an Aztec deity with multiple aspects, governing the winds, air, and the breath of life in his aspect as the god Ehēcatl, but also incarnate in the historical Toltec hero Topiltzin Cē Ācatl, who is Mesoamerica's main culture hero and known for his religious reforms and achievements as ruler of Tollan. Topiltzin was eventually forced into exile due to an alcohol-related scandal and is thought to have resettled in Central America, perhaps intending to return eventually and reclaim his kingdom. (Reports of there having been a supposed prophecy that a white, bearded Quetzalcoatl would return from the East by sea on the same calendar day that Cortés happened to arrive have little credibility, such retroactive, fatalistic prophecies having all been written by Spanish-born authors decades after the conquest.)
The foremost among all Mesoamerican feathered serpent deities, Quetzalcoatl began as a rain god and gradually came to be one of the most important deities and culture heroes in Aztec society. Quetzalcoatl and Tezcatlipoca are the sons of the creator-god Ometecuhtli or Tonacatecutli; his mother is usually listed as Coatlicue. Alternate sources list Quetzalcoatl as the son of Tonacatecutli and his consort Tonacacihuatl, or as the son of the heavenly deity Mixcoatl and the moon and love goddess Xochiquetzal.  Quetzalcoatl was associated with the morning star, while his twin brother Xolotl was thought to represent the evening star.
In Aztec culture, Quetzalcoatl was commonly syncretized with the wind god Ehecatl, who as an aspect of Quetzalcoatl was responsible for providing life-giving breath.  The association of Ehecatl with Quetzalcoatl is not definitively dated; it may come from early in the development of this figure, or it may have been a later Postclassic amalgam. As a separate deity, Ehecatl is a wind god often associated with Tlaloc, and is further listed as the ruler of the trecena (thirteen-day period) 1 Jaguar, whereas Quetzalcoatl is associated with the trecena of 1 Ocelotl. 
Quetzalcoatl’s role in Mesoamerican cultureEdit
While better known as a wind deity, Quetzalcoatl originated as a water god. In one early myth, he is called "Precious Serpent" and was described as "the spirit of the waters which flowed along the winding bends of rivers" (Fernandez 68).
Quetzalcoatl is also associated closely with the serpent cults of Mesoamerica. The cult of the serpent in Mesoamerica is very old; there are representations of snakes with bird-like characteristics as old as the Olmec preclassic period (1150-500 BC). In the murals of Teotihuacan (around 150 BC), the snake symbol began to be shown with the precious feathers of the Quetzal bird, highly prized by pre-contact peoples. The most elaborate of such representations come from the old Quetzalcoatl Temple around 200 BC, which show a rattlesnake with the long green feathers of the quetzal. 
As his cult grew, Quetzalcoatl came to be associated with the creator-deities and was ultimately named as a god of kingship and ancestor of the Mesoamerican peoples. Prior to assimilation by the Aztecs, the political class in the city of Xochicalco (700-900 AD) began to claim that they ruled in the name of Quetzalcoatl, and depictions of the god began to include more human characteristics. The Toltec rulers also used the name of Quetzalcoatl, representing him as a man with god-like attributes; these attributes were also associated with their rulers. The Toltecs would associate Quetzalcoatl with their own god, Tezcatlipoca, and make them equals, enemies and twins (ibid).
Quetzalcoatl’s role in Aztec cosmogonyEdit
Quetzalcoatl played two important roles in Aztec culture. He was first a creator deity, responsible for creating the cosmos along with his sometimes-rival Tezcatlipoca or his counterpart, Huitzilopochtli. As a creator god, he instituted the laws of death and rebirth: as such, he is also associated with agriculture and is the patron deity of chocolate. 
In Mesoamerican myth Quetzalcoatl is also a mythical culture hero from whom almost all Mesoamerican peoples claim descent; this figure was probably based on a historic ruler, and sometimes appears as Topiltzin Quetzalcoatl (Topiltzin meaning "Our Prince") or as Ce Acatl (1 Reed) (Read and Gonzalez 225). This is almost certainly an ancient association dating back to the Toltec culture; Ce Acatl Topiltzin was named as a Toltec leader and high priest of Quetzalcoatl celebrated for his military conquests in campaigns against the Mayans. 
Myths of Quetzalcoatl as a culture-hero sometimes go so far as to state that Quetzalcoatl named the mountains and seas, domesticated animals, discovered maize, established the Maguey culture, invented music and dance, established the priesthood, cured infertility and illness, and taught the art of curandero (a sort of medical divination). 
Myths of QuetzalcoatlEdit
In the Aztec creation myth, Quetzalcoatl and Tezcatlipoca fight violently over the creation of the world; first Quetzalcoatl defeats Tezcatlipoca, then Tezcatlipoca defeats Quetzalcoatl. With each victory a world age is ended; Tezcatlipoca’s victories signify the end of the second and fourth suns, so that Quetzalcoatl may return at the end of the fifth and final sun to triumph at the ending of the world. (Read and Gonzalez 223) This version of the creation myth would play an important role in culture contact with the Europeans and the eventual conquest of Aztec lands.
In another version of the creation myth, Quetzalcoatl and Tezcatlipoca cooperate, creating fire, the first sun, and the first people, creating the rain gods, and setting the god and goddess Mictlanteuctli and Mictlancihuatl in the underworld (ibid).
Another myth from the Florentine Codex describes how Quetzalcoatl set the sun in its course: Quetzalcoatl and Red Tezcatlipoca postulated that the sun should come from the East. To move the sun, the gods took a rabbit and hit it, dimming its brilliance. The sun, however, had not moved, so the gods decided to kill themselves in order to make him move. The sun still refused to move, so Quetzalcoatl gathered all of his strength and blew such a fierce wind that the sun was blown on the right course.
As a trickster god, Quetzalcoatl is known to change shape, and sometimes makes mistakes in the creation: he has to trick Mictlanteuctli when obtaining the bones to make people, and immediately upon obtaining them, he falls into a pit and jumbles the bones of men and women. He also plays a trickster's role in dispersing corn and grain to humanity: here he changes himself into an ant in the hopes of stealing the mountain where the world's grain is stored, but is unable to move it, and so instead the grain is dispersed across the earth by the lesser gods of wind and rain. (Read and Gonzalez 224)
As a culture hero, Quetzalcoatl (or Topilzin Quetzalcoatl) was said to be extremely wise, and according to myths, under his rulership agriculture flourished, goods were plentiful, and people lacked for nothing. These tales show Quetzalcoatl as the model of good rulership and the Toltecs as the model of good society. However, the myths go on to tell how Topiltzin Quetzalcoatl became complacent and neglected the Toltecs, allowing them to become fat and lazy, and eventually leading to their downfall (ibid).
Quetzalcoatl and Cortés Edit
Much of the idea that Moteczuma saw Hernándo Cortés as the returning Quetzalcoatl can be traced back to the Florentine Codex, written down some 50 years after the conquest of the Aztec Empire. In the codex's description of the first meeting between Moteczuma and Cortés, the Aztec ruler is described as giving a prepared speech in classical oratorial Nahuatl, a speech which as described verbatim in the codex (written by Sahagún's Mexica-Tlatelolca informants who were probably not eyewitnesses of the meeting) included such declarations of seeming divine or near-divine admiration as, "You have graciously come on earth, you have graciously approached your water, your high place of Mexico, you have come down to your mat, your throne, which I have briefly kept for you, I who used to keep it for you," and, "You have graciously arrived, you have known pain, you have known weariness, now come on earth, take your rest, enter into your palace, rest your limbs; may our lords come on earth." Subtleties in, and an imperfect scholarly understanding of, high Nahuatl rhetorical style make the exact intent of these comments tricky to ascertain, but ethnohistorian Matthew Restall argues that the speech, conveniently interpreted by the Spaniards as Moteczuma politely offering his throne to Cortés, may well have been intended to mean the exact opposite of what the Spaniards took it to mean, since politeness in Aztec culture was a way to assert dominance and show superiority. This speech, which has been widely referred to, has been a factor in the widespread belief that Moteczuma was addressing Cortés as the returning god Quetzalcoatl. 
Worship of QuetzalcoatlEdit
The cult of Quetzalcoatl was widespread across the Mesoamerican world, including temple centers in such cities as Teotihuacan, Tula (or Tullán, capitol of the Toltecs in middle Mexico), Xochilco, Mexico-Tenochtitlan (the central part of current Mexico City), and Chichen Itza. The highest Aztec priests were each called “Quetzalcoatl” in honor of the god. 
Quetzalcoatl was also the patron deity of the Tlaxcalan-held city of Cholula, the second largest city in Mesoamerica at the time, and his holiest shrine was located there, set atop what was then and is still the largest pyramid in the world. While ritually associated with the color white, in this iconography, his body is traditionally painted black in accordance with the priesthood he established. 
Unlike most Mesoamerican deities, Quetzalcoatl was thought to oppose human sacrifice, although animals—particularly butterflies offered alongside flowers—were sometimes sacrificed in his name. 
- Fernandez, Adela. Pre-Hispanic Gods of Mexico. Mexico City: Panorama Editorial, 1984.
- Read, Kay Almere, and Jason Gonzalez. Mesoamerican Mythology. Oxford University Press, 2000.