The Black 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. Of the sol niger he writes:
The body must be dissolved in the subtlest middle air: The body is also dissolved by its own heat and humidity; where the soul, the middle nature holds the principality in the colour of blackness all in the glass: which blackness of Nature the ancient Philosophers called the crows head, or the black sun. The black sun is used to illuminate the dissolution of the body, a blackening of matter, or putrefaction in Splendor Solis, and Johann Daniel Mylius’s Philosophia Reformata.