The last pre-Columbian civilization to enter the Valley of Mexico after the collapse of the Toltec civilization in c 12 AD, who built a magnificent capital at Tenochtitlán and were later conquered by the Spaniards (1521). They called themselves the Mexica or Tenochca and were the dominant political group of the Late Post-Classic Period. The people spoke Nahuatl. Their origin is obscure, partly because of the deliberate destruction of their own records, but tradition says that in 1193 AD the last of seven Chichimec tribes left Aztlan , a mythical birthplace somewhere north or west of Mexico, and filtered south. For a while they lived around Lake Texococo, but in 1345 they were allowed to found Tenochtitlán (under present-day Mexico City) on some unoccupied islands. By 1428 Tenochtitlán, Texococo, and Tlacopan formed an independent state which controlled most of present-day Mexico from the desert zone in the north to Oaxaca in the south, with extensions as far as the Guatemalan border - all through military expansion. By inclination and training the Aztecs were militaristic, and a person's status depended on his success as a warrior. The chief god of the Aztecs, Huitzilopochtli, was a war god who required the blood of sacrificial victims, and only constant warfare supplied the altar of the god. Human sacrifice was necessary also to ensure the daily rising of the sun. Other major deities were Huitzilpotchtli (the warrior god and chief deity of Tenochtitlan), Texcatlipoca (god of night, death and destruction), Xipe Totec (god of spring and renewal), and Quetzacoatl, the plumed serpent (god of self-sacrifice and inventor of agriculture and the calendar). Tenochtitlán became a great imperial city, so large that it could not be self-sufficient but had to rely on tributes from its provinces. Luxury goods and necessities were brought to the city, and craftsmen produced jewelry, turquoise mosaics, featherwork, and carved stone. Mold-made clay figurines were common, and the black-on-orange pottery was decorated with geometrical designs and stylized creatures. Little architecture or painting survived the Spanish conquest of 1521. Copies of several books have been preserved (as the Dresden Codex). Aztec society was set in a clearly defined hierarchical class system. At the top was the ruling class (pipil) from whom and by whom the emperors were chosen. The mass of the population were freeman (machuale) and under them were the serfs (mayeques) and then at the bottom the slaves. Most people were of the landholding group called the calpulli, which had its own internal hierarchy. Change of social class was possible through state service in the military and sometimes through merchant activity. The merchants (pochteca) served as early-reconnaissance and espionage groups. The arrival of the Spaniards and the fall of Tenochtitlán after a 90-day siege marked the end of Aztec dominance.