The traditional explanation for the origin and initial population of the universe in classic Greek myth comes from old Hesiod the poet; though quite how he derived his information is anyone's guess. In fact Hesiod was actually unaware of some of the most powerful of Olympian deities. Nonethless his are the major writings on the subject.
    However, another explanation - the Orphic Cosmology - introduces us to the powerful God of Light: Phanes.

Among the Orphic proposals (Orphic as in the writings of Orpheus) the first principal power in the universe was Cronos or Time, from whom came Chaos and Ether, respectively representing the infinite and the finite. Chaos and Ether, enveloped in the shell of Night, organised matter. From this great cosmic shell was formed the first being - Phanes, Light. 

"Thank you for welcoming me. Not many mortals knew of me in the past and my name has not been mentioned for a long time."
    The God Phanes chooses to appear as a young man in his 20s. He has short curly hair, silver eyes, and silver glistening eyebrows. Most times he appears naked, but his body is a dazzling mass of light and sparks. His light is so dazzling it almost hurts the eyes.

"I am Phanes, a mighty God. I am pleased to spend a few moments of your time with you.  Thank you for the homage you pay me. This I appreciate. 
    Not many mortals know my name, or that I exist at all. This does not trouble me as I know all will know of me, there will be temples and shrines built just for me all over your world. 
    Although I am an unknown God, my presence now is felt in temples in different parts of your world. A world that is corrupt and ugly in so many ways, yet also beautiful. One day beauty will reign, ugliness will be gone. There will be no wars, all will live peacefully. It will not be so long.

I have taken more temples, large and small and send beams of light that those who are within feel my presence. In a large temple in what you call Scotland I spoke to a woman at some length and she fainted. She told those who assisted her that she had heard the voice of God, but she mentioned my name and no one had heard of me. They said she was dreaming. I shall speak to her again and again as it is easy for her to hear.

I choose temples known as Spiritualist churches. Mortals who attend are very aware and have times when they meditate. This is when I speak to them. Although only half hear, they meet at certain times to concentrate on what I have to say. Some of the descendants of these mortals, maybe grandchildren or great grandchildren, will be priests and priestesses of the Olympian Faith."  

Temple Diaries: Phanes and the Festival of Flowers

Festival of Phanes: 30th June