Chaos

In Greek mythology, Chaos or Khaos is the primeval state of existence from which the first gods appeared.
Chaos was the nothingness out of which the first objects of existence appeared. These first beings, described as children of Chaos alone, were Gaia (the Earth), Tartarus (the Underworld), Eros (desire), Nyx (the darkness of the night), and Erebus (the darkness of the Underworld). Thus, at the very start of his story, Hesiod establishes the deities related to each element known to man, beginning with the primordial elements: the Earth, the starry Sky, the Sea.

Theogonia presents two ways to come to life, either by division (Gaia, Nyx), or by mating. After Gaia, almost all the deities brought to life by division are negative concepts (Death, Distress, Sarcasm, Deception, and so on) and for the most part, they are produced by the goddess Nyx. From this point on is set the model for reproduction, from the action of two entities, male and female, as it appears in the divine world in response to human society. So the first answer by the myth to the question "What is the cause of this?" becomes "This is the father and this is the mother".
Furthermore, all deities generated by division almost never become allies with those of male-female lineage.

Ovid, in his Metamorphoses, described Chaos as "rather a crude and indigested mass, a lifeless lump, unfashioned and unframed, of jarring seeds and justly Chaos named". From that, its meaning evolved into the modern familiar "complete disorder", and the word "Chaos" is used by astronomers in Mars place names to mean "area of disorderly faulted terrain".

Chaos features three main characteristics:
it is a bottomless gulf where anything falls endlessly: That the Earth will emerge from it to offer a stable ground, radically contrasts with Chaos;
it is a place without any possible orientation, where anything falls in every direction;
it is a space that separates, that divides: after the Earth and the Sky parted, Chaos remains between both.

In Ancient Greek Cosmology Chaos was the first thing to exist and the womb from which everything emerged. For Hesiod and the Olympian Mythos, Chaos was the 'vast and dark' void from which the first deity Gaea emerged. In the Palasgian Creation Myth, Eurynome ('goddess of everything') emerged from this Chaos and created the Cosmos from it. For the Orphics it was called the 'Womb of Darkness' from which the Cosmic Egg that contained the Universe emerged. Sometimes conflated with 'Black Winged Night'.

The idea is also found in Mesopotamia and associated with Tiamat the 'Dragon' of Chaos, from whose dismembered body the world was formed.

Primal Chaos was sometimes said to be the true foundation of reality, particularly by philosophers such as Heraclitus and those trained in 'Orphic' schools. It was the opposite of Platonism. It was also probably what Aristotle had in mind when he developed the concept of Prima Materia in his attempt to combine Plato with the Presocratics and Naturalists. It was a concept inherited by the theory of Alchemy.
It has more recently been revived in Chaos Magic.


Erebus

In Greek mythology, Erebus, or Érebos was a primordial god, personification of darkness, offspring of Chaos alone. He was brother of Nyx and father of Aether by himself and, with Nyx, Hemera, Moros, Charon, Eros and the Keres.

According to some later legends, Erebus was part of Hades, the underworld. It was where the dead had to pass immediately after dying. After Charon ferried them across the river Acheron, they entered Tartarus, the underworld proper. Erebus was often used as a synonym for Hades, the Greek god of the underworld. Also, Erebus was the name of the gloomy space through which souls passed on their way to Hades.