 He was also the secondary Week God for the tenth week of the twenty-week cycle of the calendar, joining the sun god Tonatiuh to symbolise the dichotomy of light and darkness.In the Colonial Codex Vaticanus 3738, Mictlantecuhtli is labelled in Spanish as "the lord of the underworld, Tzitzimitl, the same as Lucifer".In Aztec mythology, after Quetzalcoatl and Tezcatlipoca created the world, they put their creation in order and placed Mictlantecuhtli and his wife, Mictecacihuatl, in the underworld.