Satan encompasses all of the "zodiac" energies and he is beyond these. Darkness is the testament to learning and accepting that there are unlimited veils humans can overcome. Aside from the basic understanding of darkness and light, these are occult meanings and pursuits. When you meditate, you enter the darkness, in the unknown. The path to Godhood is an unknown and mysterious path due to circumstantial existence and the sacred path it entails. It stimulates basic principles within the human mind such as bravery, the quality of discernment, and structuring. This is all around the spiritual side.
Satan has also been surrounded by blasphemy and perversion by the enemy on this Earth, and turning the "darkness" and the "fountain of the aether" into something primal and imprisoning the consciousness into a low response of survival. Darkness is not evil, and darkness is not just the concept of darkness or the absence of light. For example, humans can see a very small part of the visual spectrum, this related to the above - to the human limitation and condition, by entering the darkness we overcome it, as we overcome our limitation of sight (consciousness).