Mythology & Beliefs: Chaos In Greek and Roman Mythology, Chaos was a formless void; personified as first of gods.
Chaos in Greek and Roman Biography and Mythology
（*Xa/os), the vacant and infinite space which existed
according to the ancient cosmogonies previous to the creation
of the world (lles. Thmeog. 116), and out of which the gods,
men, and all things arose. A different definition of Chaos is
given by Ovid (Ov. Met. 1.1, &c.), who describes it as the
confused mass containing the elements of all things that were
formed out of it. According to Hesiod, Chaos was the mother of
Erebos and Nyx. Some of the later poets use the word Chaos in
the general sense of the airy realms, of darkness, or the
lower world. - A Dictionary of Greek and Roman biography and
mythology, William Smith, Ed.
Chaos in Wikipedia
Chaos (Greek χάος khaos) refers to the formless or void state
preceding the creation of the universe or cosmos in creation
myths, particularly Greek but also in related religions of the
Ancient Near East. The motif of chaoskampf (German for
struggle against chaos) is ubiquitous in these myths,
depicting a battle of a culture hero deity with a chaos
monster, often in the shape of a serpent or dragon. He is
known as the god of darkness...