Which primordial deity represented night?

The primordial deity who represented night was Nyx.

Nyx is the ancient Greek personification and goddess of night. In Hesiod’s Theogony, she emerges from Chaos and belongs to the earliest generation of divine beings. Her counterpart and consort is often Erebus, the personification of primordial darkness; together they produce Aether, the upper brightness or sky, and Hemera, the personification of day.

Nyx also produces many powerful personifications on her own, including Hypnos, sleep; Thanatos, death; Nemesis, retribution; Eris, strife; and the Moirai, or Fates, in some traditions. These genealogies make night a source not only of darkness but also of forces governing sleep, mortality, conflict, and destiny.

Poets often place Nyx at the edges of the world, where night and day pass one another. Homer presents her as an ancient power whom even Zeus is reluctant to offend. Later Orphic traditions sometimes elevate her further, presenting Night as the first deity or as a cosmic mother. Nyx is commonly confused with Hemera, but Hemera represents day, while Erebus represents darkness rather than night itself.