The sun and the moon were thought to be "portals" to either Paradise or Purgatory (reincarnation).
Fire,
light, daytime, the bright lunar fortnight, and the six months of the northern
solstice of the sun; departing by the path of these gods the yogis, who know
Brahman, attain nirvana.
Bhagavad-Gita 8.24
Smoke, night, the dark lunar fortnight, and the six months of southern solstice of the sun; departing by these paths, the righteous person attains lunar light and reincarnates. Bhagavad-Gita 8.25
The sun is a representation of the Spiritual Sun, the source and Home of all Light.
The moon is like a mirror, reflecting ascending light (deceased souls) back to Earth.
The moon is connected to Diana, or Danu the goddess of witchcraft, who wears a moonsickle on her head.
.