And Eternity by Piers Anthony

knew she was losing.
    Then a cloud formed, not black but white, its vapors swirling internally. “What is this?”
    “Nox!” Jolie cried, recognizing the strange, soundless way the Incarnation spoke. She had never seen Nox before, but Parry had described it.
    Orlene paused, looking up. “The bitch is here?”
    “Come to me, man-thing.”
    Orlene got up. She stared at the Incarnation. The mists formed into a phenomenal woman-shape, naked and beckoning, with writhing tresses of vapor and two compelling dark eyes.
    Orlene walked into the shape, embracing it. Her loins thrust and thrust again, and the form wrapped itself about her. The face kissed her ardently. The merged forms floated from the ground, not noticing in their preoccupation.
    Jolie’s amazement was admixed with disgust. Orlene had tried to rape her, and now was having sex with Nox! How could she ever forgive either of them for such a thing? She had only tried to help a woman find her lost baby!
    “There is much you do not understand” Nox said to her directly.
    “There is much I do not care to understand!” Jolie retorted, made bold by her shock.
    “Here is part of it.”
    Then Orlene emerged from the white cloud, her female form restored. She stood there, her mouth opening in an ‘O’ of wonder, horror and dismay.
    Simultaneously, Jolie felt herself change. Suddenly she lusted after the woman who stood before her, her passion so compelling that it admitted of no interference. She strode toward Orlene.
    Only to be intercepted by the cloud. “Love me instead,” Nox said. Her female aspect was the most utterly arousing and inviting thing imaginable, making any human body hopelessly crude and clumsy.
    Jolie stepped into it, her member stiffening. She plunged into Nox, and found herself floating, unable to achieve the culmination. The frustration was maddening.
    Then the cloud dissipated, depositing her on the ground. “Remember!” Nox cautioned.
    The two women stood looking at each other. Both were fully female again, each appalled.
    “Oh, Jolie,” Orlene said. “I don’t know what, I cannot ask you to forgive me, I am so ashamed-”
    Understanding was coming. “Nox made you into a man,” Jolie said. “And you were overwhelmed by male passion.”
    “But you were my companion, my friend! How could I-”
    Jolie would not have understood, except for the brief lesson Nox had given her. If Orlene, unwarned, had run rampant, what of Jolie, who had seen it all, and run rampant herself the moment the Incarnation afflicted her with the same complaint? She was the one who truly knew better, yet she had been helpless before her abrupt desire.
    “It seems that men have passions that women do not,” Jolie said. “I have indulged those passions in my own man without ever really understanding their nature, until now.”
    “But men do not-” Orlene faltered, unable to say the word.
    “They have learned control. We did not have time. Like a fire which burns out of control when untended-”
    “Remember,” Nox repeated, her semblance returning.
    “How can I endure this shame?” Orlene exclaimed and collapsed.
    Jolie ran to her, finding her unconscious. For the moment, that was a relief. “Why did you play with us, Incarnation of Night?” she asked, no longer concerned about manners.
    “You have much to learn.” That, it seemed, was the extent of the answer they were to have.
    “She came to recover her baby, Gaw-Two,” Jolie said. “Please, Incarnation, return him to her, now that you have humiliated us.”
    “I have her baby,” Nox agreed. “I lent her his semblance as he will be when grown.”
    Orlene, stirring, reacted as if struck. Jolie, appreciating her horror, interceded. “A man-like his father.”
    “No!” Orlene cried in anguish. “Norton is not like that!”
    “Like Gawain!” Jolie exclaimed, catching on. “His genetics were changed!”
    “Like Gawain,” Nox agreed. “As he will be, grown naturally.”
    “But he died of a