In Greek mythology, Nyx is the personification of darkness. In particular night. Nyx was born directly from the void of Chaos, and was the one of the first Protogenoi. She was married to Erebus (Primordial God of Depth) who is also her brother and had many children with him. She is an incredibly powerful divine being, as she was a Protogenoi.
A myth that supports her power is when Hypnos, the minor god of sleep and her son, fled Zeus because he put him to sleep on Hera's orders, so she could give great misfortune onto Hercules. Zeus found out about his involvement and chased him. Hypnos fled to his mother Nyx whom Zeus obviously feared as he held his anger at bay, not wishing to offend Nyx. Another myth is that Nyx's daughter, Hemera (day) left Tartarus when Nyx entered it, creating night and day.
According to some Greek articles Chaos did not exist and Nyx, in fact, was the first divine Entity, promoting her power and importance even more. Her son Moros (Doom) is mysterious as well, and is believed to be omniscient, omnipresent, and omnipotent, as he drives all things to their ends. One example is that Zeus cannot defeat her, another being that the Moirae (Fates) serve him.
Nyx is the Greek word for night. This goddess had many cults around Ancient Greece and Rome but she had more cults than Temples. Nyx had many priests who worshiped in her name, all her followers worshiped at night in complete darkness. The Night Mother had two major cults in Antient Greece; these were Megara located in Megaris (Southern Greece) and one in Rome the Capital City of the Roman Empire.
Evey day, Nyx was residing in her home all day long, taking care of her fifteen dark spirited children, among them Hypnos (the sleep) and Thanatos (the death). By the evening, Nyx was leaving her home to set off for her nightly jouney. On her way she met Hemera, the Day, who was returning home from her daily trip and they were greeting each other peacefully. When she flew across the sky bringing darkness she would leave a trail of glitterling stars that would disappear once she would return to her Mansion of Night.
She was depicted as riding in a chariot, trailing stars and bringing the night, and accompanied by Her sons Hypnos and Thanatos. She could be helpful or harmful to mankind, bringing either sleep or death. Nyx had prophetic powers, and gave oracles from a cave. She was older and more powerful than Zeus, who deferred to Her wishes.
In Roman mythology Nox is the goddess of night and darkness and sometimes associated with witchcraft.