According to Egyptian myth, when Ra became too old and weary to reign on earth he relinquished and went to the skies. Ra was said to travel through the sky on the barge, providing light to the world. Each twelfth of his journey formed one of the twelve
Egyptian hours of the day, each overseen by a protective deity. When the sun set and twilight came, he and his vessel passed through the
akhet, the horizon, in the west, and traveled to the underworld. with each hour of the night considered a gate overseen by
twelve more protective deities. Every night enormous
serpent Apophis, the god of chaos (
isfet) attempted to attack Ra and stop the sun-boat's journey. After defeating the snake, Ra would leave the underworld, returning emerging at dawn, lighting the day again. He was said to travel across the sky in his falcon-headed form on the Mandjet Barque through the hours of the day, and then switch to the Mesektet Barque in his
ram-headed form to descend into the underworld for the hours of the night. The progress of Ra upon the Mandjet was sometimes conceived as his daily growth, decline, death, and resurrection and it appears in the symbology of Egyptian mortuary texts. == Funerary practices and religion ==