Nyx, goddess of night and spirits. Means "night" in Greek.
Nyx, primary benevolent deity in PC Cast 'House of Night' series
Nyx, Infamous 2 (video game) character.
Nyx, character in RickRiordan's "Heroes of Olympus" series
NyxUlric, male character in the movie "Kingsglaive: Final Fantasy XV"
To nix something is to say no to it