In the House of Night novels, Nyx is the goddess that all the vampyres worship.  She is the goddess of night and has many different names and seems to show up across multiple religions.  Even the nuns that work at Street Cats believe that Nyx is just another name for the Virgin Mary.  To most characters in the series, Nyx is an obscure figure but to Zoey and a few other characters, she actually speaks and even occasionally appears.  She is also the one that gives the vampyres and fledglings gifts which she say she can never take back.

In Greek mythology, Nyx is a goddess that is the personfication of night.  Her name in Roman mythology is Nox.  Nyx came from the black void known as Chaos along with Erebus (as in the sons of Erebus in House of Night) and a few others, including Gaia, who became the mother of the titans.  Erebus is the personification of darkness.  Erebus and Nyx mated.  Their children included the personification of sky, day, Nemesis and Charon, the ferryman across the river Styx to Hades. 

It has been years and years since I’ve read Theogony by Hesiod so someone correct me if I get this wrong.  Nyx produced children asexually as well.  These included Doom, Fate and Death (sometimes written out as Fate of Death), Dreams, Blame, Woe, Hesperides (who guards a garden in the corner of the earth that we see in the Hercules myths), Age, Strife, Friendship, Deceit, and possibly some more that I forgot.  Wikipedia list some more that I can’t remember ever learning about in mythology so I’m not sure.  It also list her as mother of the hellhounds.  Not sure on that one.

Nyx, along with Erebus and most of her children are considered personification gods.   This is a statement true of many gods and goddess in mythology.  It is exactly what it sounds like.  They are an abstract like love, darkness, night, dreams, and so on put in human form.  An example of a non personification god would be Hades who is god of the underworld or Zeus, god of the gods.   Think about it this way, Nyx is consider to actually be night rather than the goddess of the night.

In many different myth, Nyx is seen as living in a cave often at the end of the ocean.  She is also sometimes seen as just being a dark mist.  Hmm, that sounds familar.  Zoey in the House of Night novels sometimes travels that same way. 

As for Greek religion, Nyx is persent but not really a main focus.  I’m not familar with their being any temples of Nyx.

Okay now to the modern.  NYX was the name of a comic that ran for a couple years that was an offspin from X-Men.  There was only a handful of issues made.  The comic has nothing to do with the Greek myth though.  NYX means New York District X.

Nyx is also the name of one of the bio weapons that shows up towards the end of the video game Resident Evil Outbreak.  Again, I don’t see any relation to Greek myths.