In Aztec mythology, the lord of the underworld is Mictlantecuhtli. He is depicted as a skeletal figure adorned with various symbols associated with death and the afterlife. His domain is Mictlan, the place of the dead, where souls journey after death. Mictlantecuhtli oversees the transformation of souls through the underworld, emphasizing the importance of respecting death in Aztec culture. He often appears alongside his wife, Mictecacihuatl, and is integral to Aztec beliefs about mortality and the afterlife.