The Protogenos, or the Greek Primordial Gods, were the first Gods that appear in the Protogenos Arc series and therefore inflict unknowingly change on the entire of the Saint Seiya series. The Protogenos are often divided into two forms, one part Divine and one part personification (e.g. Gaia is a Goddess and the Earth), at the same time.
The Protogenos are Primordials with near limitless power in all realms of existence but are practically invincible within their home realms, an example of this was that Gaia was cast into Tartarus and trapped there because she was too powerful to be defeated while standing upon the Earth which she is the Goddess and personification of, the two unique Protogenos were Chaos and Tartarus as they both have rather excessive domains being considered the true Primordial Gods.
The last Primordial Gods to go to sleep or fade away were Tartarus, Gaia, Ouranos and Pontos. Incidentally, Tartarus believed that by usurping dominion of the Heavens that it was Ouranos' fault that Chaos had gone into an eternal sleep, Tartarus became the leader of the first Holy War to destroyed the World facing off against Gaia whom defended her husband.
Gaia had Pontos and the Titans fighting for her, whilst Tartarus had the Primordial deities: Thanatos and Hypnos, additionally Tartarus' first defeat caused Tartarus to sacrifice his body to create the Stormy Hell Pit of Tartarus which became the core of Tartarus' domain. Within the Walls of Tartarus that acted as a two-way barrier against intruders and defended Tartarus' palace, there Kronos, Pontos and their parents battled a weakened Tartarus whom lost his physical form from the combined attack of four blasts of pure Dunamis each from Gaia, Ouranos, Pontos and Kronos. Despite his consciousness fading and fading into the Darkness he created, Tartarus swore that he would one-day return, laughing madly which Gaia said sounded "sad" and "lonely".
By Saint Seiya's Hades Arc, the legacy of Tartarus and the Protogenos once again becomes a big event, by the Heaven Arc the Protogenos have been recruiting and have gathered a sizeable number of their reincarnations and loyal servants, by Saint Seiya Omega the Protogenos eventually return and announce their rejection of Mars' goals.
- Chaos - Chaos is the Arche of the Primordial Gods, the first and Sovereign of the Primordials and came to be the empty space from which the Big Bang had occurred, Chaos is the god of the Void, Heavens, Sky, Existence and Creation. Everything in space is part of his domain, including time itself, a piece of Chaos is found in all cosmo and the human soul (Anima) was a gift from Chaos to humanity. Chaos is later revealed to be reincarnated in Seiya.
- Tartarus - Tartarus was born from the Chaos of the Big Bang shortly after Chaos and came to represent his other half, Tartarus represented destruction and death, Tartarus was the void outside of the Galaxies - the gap between entire worlds. The Gift Tartarus gave humanity was the Collective Unconsciousness (Animus) which eventually formed the consciousness of humanity, however it was as much a curse as a gift, while it gave humanity independent free will and a sense of unity at the same time it also gave Humanity the potential to make mistakes and do evil deeds. Tartarus is later revealed to be reincarnated in Kay.
- Gaia - Gaia is the God and Personification of the Earth,
- Thanatos - Thanatos is the God and Personification of Death.