The Black Sun

Akast the Black Star, the Invisible Sun, the Sun of Many Colors, the Central Sun, the Midnight Sun.
In alchemic and Hermetic traditions, suns () are used to symbolize a variety of concepts, much like the sun in astrology. Suns can correspond to gold, citrinitas, generative masculine principles, imagery of "the king", or Apollo, the fiery spirit or sulfur,[1] the divine spark in man,[2] nobility, or incorruptibility. Recurring images of specific solar motifs can be found in the form of a "Dark" or "Black Sun", or a green lion devouring a sun.
Sol niger (black sun) can refer to the first stage of the alchemical magnum opus, the nigredo (blackening). In a text ascribed to Marsilio Ficino three suns are described: black, white, and red, corresponding to the three most used alchemical color stages.
The Black Sun in Mesoamerican mythology has many mystical meanings, among them it is connected to the god Quetzalcoatl and his penetration in the Underworld through the west door after his diurnal passage on the sky. For the Mexicas there were two suns, the young Day Sun and the ancient Dark Sun. Some scholars regard the mythological Black Sun as the ancient female origin of all, it is both tomb and womb. This way, it is the oneness that uniformly integrates unawareness, death, and yet an expectation of fecundity.[1] The Aztecs associated the passage of the Black Sun, on its nightly journey through the underworld, with the image of a butterfly.[2][3] 
The term Black Sun (German Schwarze Sonne), also referred to as the Sonnenrad (German for "Sun Wheel"), is a symbol of esoteric and occult significance. Its ancient design is also found on a sun wheel mosaic incorporated into a floor of Wewelsburg Castle during the Nazi era.