Historia general de las cosas de nueva España (General history of the things of New Spain) is an encyclopedic work about the people and culture of central Mexico compiled by Fray Bernardino de Sahagún (1499–1590), a Franciscan missionary who arrived in Mexico in 1529, eight years after completion of the Spanish conquest by Hernan Cortés. Commonly referred to as the Florentine Codex, the manuscript consists of 12 books devoted to different topics. Sahagún followed the typology of earlier medieval works in organizing his research into “the divine, human, and natural things” of New Spain and addressing these topics in order. Book I thus deals with the gods. It describes the principal deities in the Aztec pantheon, listing their distinctive physical features, attire, main functions, and the festivals dedicated to them. To make these gods more comprehensible to European readers, Sahagún sometimes likens them to figures from Greek and Roman mythology. Huitzilopochtli (“Uitzilobuchtli” in the codex) is called “another Hercules,” Tezcatlipoca “another Jupiter.” Huitzilopochtli was the patron god of the Aztecs, who guided them on their pilgrimage from Aztlán, the mythical “white land” of their origins, to the “promised land,” where in 1325 they founded the city of Tenochtitlan. He was the god of war and of the sun, huge, immensely strong, and warlike, and to him was dedicated one of the two shrines of the Templo Mayor (Great Pyramid) of Tenochtitlan. The other shrine was dedicated to Tlaloc, the lord of rain, who lived on the highest mountains where clouds form and was associated with the agricultural world and the fertility of the land. Huitzilopochtli, Tlaloc, and two other major gods are depicted on folio 10r. For Sahagún, religion was the key to Aztec civilization. As he wrote in the prologue to Book I, “in religion and the adoration of their gods, I do not believe that there have ever been idolaters more devoted to their gods, nor at such great cost to themselves as these [people] of New Spain.”