Mistress Nyx appears to be a small Asian woman in her early forties. Her diminutive appearance is deceptive. She is unexpectedly strong and adept in multiple forms of martial arts.
Mistress Nyx' back story was revealed in Carnal Invasion VI: The Dark Delights of Mistress Kali.
The pod containing the creature which would become Mistress Nyx landed near a "comfort station" in the Philippines in World War II. There she encountered a badly burned woman whose life she tried to save. As the woman's spirit departed her fatally damaged body, the newly arrived Gamma Iridian assumed her appearance to honor her.
As it happened, Ulrich, Samantha, and Mistress Kali were on a mission to rescue the women imprisoned at the comfort station. Mistress Kali sensed the presence of another of their kind, and as Ulrich and Samantha distracted the soldiers, Mistress Kali made her presence known to the frightened traveler. It was Kali who gave Mistress Nyx her new name. Kali admonished Nyx to stay hidden until she returned for her.
Nyx' curiosity got the better of her, and she looked into the window of the comfort station, where Ulrich, Samantha, and Kali had hypnotized the soldiers to have sex with one another while they rescued the comfort women. Nyx became aware that erotic energy could empower her, but she was so disgusted by what had been done to the being whose form she had assumed that she swore she would die before ever accepting such energy.
Samantha, Kali, and a kind young Chinese woman named Zan reassured Nyx that when the erotic energy exchange was consensual, it was mutually beneficial. Nyx eventually accepted the energy her new friends offered. Although she and Zan never exchanged erotic energy again, Nyx and Zan were great friends for the remainder of Zan's life.
Mistress Kali and Mistress Nyx have a special bond with one another. Although they broke up briefly over disagreements regarding Kali's scientific and magical activities, they reunited and have remained a couple.
Like Mistress Kali, Mistress Nyx has several cloned offspring. Unlike Mistress Kali, she does not lay an egg in which to gestate her offspring. The new offspring simply separate from her body in the manner of an amoeba. The offspring are mature adults from the time of their formation. They do not have a parent-child bond with their progenitor.
“You have come to the world on which you abandoned us and insulted us for making our way as best we could, and now you expect us to simply step in line? It does not work that way! I will require compelling reason to cooperate with you in any fashion, or you had best prepare yourself for a fight. When it comes to defending my companions, it is only fair that you should know that I fight dirty.”