Hemera

Hemera left the house beneath the earth as Nyx entered it. Daylight went out with Hemera, and night came with Nyx. The two primordial sisters passed one another at the threshold, each taking the place the other had held. Their exchange brought day and night to the world in turn.

Nyx had been born from Chaos, when land, sea, and air still lay mixed together in a shapeless mass. She later became united with Erebus, the darkness that shrouded the Underworld. Their union produced Aether and Hemera, Air and Daylight. Hemera therefore came from the darkness that preceded light, while Nyx remained the night that carried the potential of day.

Nyx lived in a palace in the dark regions of the lower world. When evening came, she left the upper world and returned to that dwelling beneath the earth. Darkness followed her across the sky and filled every void and crevice. Hemera then departed from the house and scattered the darkness of Erebus. Her coming brought daylight over the earth.

The sisters did not remain together. Hemera left as Nyx entered, and Nyx left as Hemera entered. Neither kept the world permanently, since each gave way to the other at the appointed turn. Their passage continued without end, and day and night alternated eternally.