Erebos

"Erebos, a son of Chaos. The name signifies darkness, and is therefore applied also to the dark and gloomy space under the earth, through which the shades pass into Hades." - (Hom. Il. viii. p. 368.)

Erebos was the primordial god of darkness. His dark mists encircled the world and filled the deep hollows of the earth. His darkness was what bought the night across the sky.