It's a pagan symbol related to Sun worship and it's obviously satanic. This is apparent from the last few paragraphs that claim that ultimate reality is physical and impersonal. As Christians we believe God created everything, including the laws of physics and His providence is all-encompassing. God's divine energies are also called the uncreated light. Darkness is the absence of light - it has no ontological (real) existence. It is caused by a shadow, closing one's eyes and moving away from the light by your own will. Saying darkness precedes the divine light makes no sense because nothing precedes God.

The Black Sun is ultimately a death cult, worshipping the created universe and death that is bound to be destroyed in the apocalypse, and worship of nothingness (hence the black hole and space talk). But we already know that if you don't follow Christ who is the life and the way, you're choosing death. Everyone outside of Christ's Church ultimately worships death. This is what Satan wants.

Tl;Dr it's new age esoteric neopagan nihilist bs (which explains the Nietzsche quote).