Mictlan is the underworld in Aztec mythology, serving as the final resting place for souls after death. It is believed to be a dark and challenging realm, consisting of nine layers, each with its own trials. Souls must navigate through these layers to reach their ultimate destination, where they can find peace. The journey to Mictlan is guided by Xolotl, the god of death and the evening star. He helps souls cross the river Chicunamictlan and face various obstacles, such as fierce winds and dangerous creatures. Only those who successfully complete the journey can rest in eternal tranquility.