In Greek mythology, Erebus, also Erebos (Ancient Greek: "deep darkness, shadow"), was the son of a primordial god, Chaos, and represented the personification of darkness. Erebus married his sister Nyx (goddess of the night) and their offspring include: Aether, Cer, Hemera, Charon, the Hesperides, Hypnos, the Moirae, Momus, Nemesis, Oneiroi, Phlegethon, Styx, and Thanatos. In Greek literature the name Erebus is also used to refer to a region of the Underworld where the dead had to pass immediately after dying, and is sometimes used interchangeably with Tartarus