Erebo or Erebos (Greek: Ἔρεβος, transl.: Érebos, "darkness" or "gloom") is, in Greek mythology, the personification of darkness and gloom. He has his domains demarcated by his dark, lifeless robes, predominating over the regions of space known as the "Void" just above the nocturnal robes of his sister Nix, the personification of night.
Erebo was the son of Chaos. Erebo along with his twin sister, Nix, the personification of night, were born from splits just as single-celled beings reproduce; from parts of Chaos, Erebo and Nix become the oldest immortals in the universe, right after their father.
Erebo married Nix, begetting two more primordial gods: Ether (the celestial Light) and Hemera (the Day).
Like his sister, he was capable of taking immortality from the gods. Erebo is the universe itself, lord of the cosmos and of black holes. Today, however, he is a forgotten power. He is imprisoned in Tartarus. In the past, he intended to free, alone, the titans imprisoned by the Olympians right after the Titanomachy, but fell into an ambush set by his sister.
Zeus, Hades and Nix, fearful of the power of the great primordial god and of the possible return of the titans, stopped him; the three of them, united, each using their unique powers, threw Erebo into the infernal river Aqueron, the river of death. Then, they sent the weakened body of the enemy to Tartarus, the only prison capable of stopping him.
He is known to be one of Zeus' greatest enemies. It is said that the titans asked Erebo for help and personally the primordium descended into Tartarus to free the children of Gaia, but was surprised by Zeus and Hades who had the help of Nix to throw Erebo into the depths of the river Aqueron, the border of the two worlds.
As the mythical thinking of the Greeks developed, Erebo gave its name to a region of Hades, through which the dead had to pass immediately after death to enter the underworld. After Charon had them cross the river Aqueron, they entered Tartarus, the underworld proper.
Besides Aether and Hemera, Erebo had other children with Nix. These were true and proper deities, but also personifications of abstractions, including:
Tânato - death
Hypno - sleep, twin of Tangato
Oniros - personifications of dreams
Momo - sarcasm and irony, expelled from Olympus for harshly criticizing Zeus and tenderness
Nemesis - revenge
Moros - fate
Geras - old age
Apate - the deceit
Eris - the discord
Queres - the violent death
Oizus - Misery
Filotes - Friendship