With regard to your question about the black sun, Baudelaire’s ‘soleil noir’ is by no means an exception. The idea of a counter earth occurs, for instance, in the Pythagorean system, and we find the sol niger in alchemy, also the ignis niger.
Jung’s definitive documentary statement on the Black Sun, situating the sol niger within a cross-cultural lineage spanning Pythagorean cosmology, Romantic poetry, and operative alchemy.
, Letters Volume 1: 1906-1950, 1973thesis