Rê (or Ra) is the sun god, one of the most important deities in the Egyptian pantheon. He was the creator god, responsible for life, light, and the daily cycle of the sun. Rê's daily journey was a metaphor for life, death, and rebirth. He traveled across the sky in his day bark, bringing light to the living. In the evening, he descended into the Duat (the west) in his night bark, where he confronted the forces of chaos (like Apophis) and united with Osiris (god of the underworld) to regenerate before being reborn in the east at dawn.

In ancient Egyptian cosmology, the west was intrinsically linked with death, the underworld (Duat), and the setting sun. Just as Rê set in the west each evening, the deceased were believed to "go to the west" to enter the afterlife.

For the deceased, joining Rê on his journey through the Duat was a central aspiration. By aligning themselves with Rê, they hoped to achieve regeneration and eternal life, mirroring the sun god's daily rebirth. 

Litany of Re" (sometimes spelled "Litany of Ra") is a significant religious composition from the New Kingdom, often found inscribed in royal tombs (particularly in the Valley of the Kings, starting from the reign of Thutmose III) and also on papyri for non-royal individuals.

The Litany of Re consists of a long series of invocations and hymns to the sun god Rê in his various forms and manifestations. It identifies the deceased king (or individual) with Rê and with Osiris, emphasizing their divine journey and rebirth.

It typically begins with an adoration of the seventy-five manifestations of Rê, followed by a prayer for the king to join Rê in the underworld. The text details Rê's nightly journey through the Duat, his struggle against evil, and his eventual rebirth.

The primary purpose was to ensure the successful passage of the deceased through the underworld, their unification with Rê and Osiris, and their ultimate rebirth and eternal existence.