Nyx is a beautiful Goddess and if your intrested I'll tell you the story.
Long before the gods appeared, in the dim past, uncounted ages ago, there was only the formless confusion of Chaos, brooded over by unbroken darkness. At last, though no one ever tried to explain it, two children were born to this shapeless nothingness. Night was the child of Chaos and so was Erebus, which is the unfathomable depth where death dwells.
Into the bosom of Erebus dark and deep
Laid a wind-born egg, and the seasons rolled
Forth sprang Love, the longed-for , shining, with wings of gold.'
An Exert from Mythology by Edith Hamilton
You are correct when you say Nyx is the ancient personification of Night, and Erebus her consort. The male and female. Nyx has threw the centuries been called many other things like Gaia, the Mother Earth, Medicine woman (from native American tribes) and things of the like. They were the first true Goddess and God every created. From them grew love, and was born Father Heaven and Mother Earth,(Gaea and Ouranos). and from them the first creatures born were monsters.Then the Titans then the Greek Gods like Hecate.
Now Hecate was more to be concidered the Goddess Artemis, as she was called "the goddess of three forms" Selene the sky, Artemis on earth, and Hecate in the lower world and in the world above when it is wrapped in darkness.
Hecate was the Goddess of the Dark of the Moon, the black nights when the moon is hidden. Also known at the Goddess of crossways. Though perception of her has changed, Hecate was associated with deeds done in the dark and dark magic.
That should help. But don't just take my words for it. Look into it for yourself.