Many assumed that the worst part of Luna's banishment had been the isolation and the loneliness; both were wrong, but only partially: the worst thing about being on the moon for one thousand years was the silence, for there is no sound in space.
One thousand years, with naught but the voice in her head to fill her ears.
Before her exile, the voice of Nightmare Moon in Luna's mind had been subtle. That is to say, her darker side did not speak to her; more like, it whispered suggestions through the years, slowly turning Luna into the monster that she had become.
But here, in the nights, when her sister's sun passed behind the moon and the cold was bone-deep and the darkness was so thick it felt almost like a physical entity, the resounding voice of Nightmare Moon rang through her ears, and she was helpless to stop it. The demon spoke of revenge, mostly, but sometimes felt Luna's pain, and tried to comfort her. At first, when she heard the voice, she'd cover her ears in vain and wish for the silence to come back. But after a year of this, Luna learned not to fight it. After five years, she embraced it. She found she could talk back to her dark side, literally have a conversation with herself. Nightmare Moon, the reason for Luna being on the moon in the first place, turned out to be her truest friend in her time of need.
But after a while, Luna ran out of ways to occupy herself, and her new friend. Her needs turned more physical in nature. She contemplated masturbation for some time; then on one particularly cold night, when Luna heard Nightmare moon screaming of the need to get warm, she crawled out of the alcove in the rocks that she had been using for a makeshift bed, and finally determined what needed to be done.
When Luna tentatively slipped her robes off to touch herself, it was on her own initiative. The voice had questioned her motives and well being when Luna gasped as she slid first one, then two fingers inside her sex. Her hand had instinctively gone to her breast, stroking her hardening nipple and gently squeezing.
The hot shivers that ran through her body had apparently awakened a hunger in Nightmare Moon as well, for with every time she slid her fingers in and out of her slit she heard her other half's moans burning through her mind; it made the experience all the more invigorating, for she was experiencing the pleasure of not one but two beings. Her thighs were soaked, and as she increased her speed Luna saw droplets of moisture float out into space, twinkling in the starlight. It was admittedly the most arousing thing she had ever seen. The heat spreading through her body burned like a fire, and as she rubbed her thumb over her engorged clitoris she felt her orgasm explode from her in an inaudible shriek. Nightmare Moon's scream of ecstasy was perfectly audible, however, and she watched as fluid erupted from her vulva, propelling itself out to join what moisture was already floating in the darkness. She lost all control of her limbs as she writhed in the darkness.
Only when her orgasm died and the warmth faded did she realize she was floating. The pale grey surface of the moon was about five feet below her, and with a flood of fear she realized that she couldn't get down. She waved her arms in a fashion like that of a swimmer, to no avail. She was stuck, floating in the dark, unable to reach the ground. She felt something liquid and ice-cold touch her cheek; a droplet from her own vagina. It did not arouse her now; the only emotions she felt were fear and shame. She curled into the fetal position and wept, crying herself into a cold and fitful sleep.
She woke when she felt a nudge at her shoulder. In a daze, she mouthed for her sister to go away, only to snap awake and realize that she had drifted back down to the lunar surface. She wept tears of joy, albeit bitter ones. Slowly crawling, she searched for her robe. It was nowhere to be found.
Luna was alone, naked on the surface of the moon, a million miles from home. She crawled until she located her alcove, crawled into it, and wept some more.
And then the night came.
It was not the cold that woke her, but the queer feeling of liquid running down her thigh. Confused, she wondered if she had somehow emptied her bladder in her sleep, until she heard the faint gasps inside her head. Nightmare Moon was pleasuring herself, against Luna's will, without even using Luna's hands to do it. She could feel some sort of energy inside of her vagina, working it's way back and forth. It was warm, and felt almost solid. She inwardly as it worked its way deep inside her.
Terrified of the possibility of somehow finding herself back in open space, she silently begged Nightmare Moon to stop. If anything, her pleas only increased the speed and intensity of the thrusts. Luna wanted it to stop, but the warmth spreading up her torso made it impossible to resist. She squeezed her right breast, and was delighted at how warm it seemed, her heart beating underneath the soft flesh, sending hot blood all though her body. All caution erased from her mind, Luna decided to play a bit. She took her left breast, bent her head forward and took her nipple into her mouth. Tendrils of electricity snaked through her chest as she nibbled on the sensitive rosey pink mounds on her breast, and her back arched. Nightmare Moon was taking care of her cunt, which gave Luna's hands more to do to make it even better. The zero gravity let her breast stay in place as she bit on her nipple. Her right hand was busy playing with her right breast, but her left hand snaked its way down he stomach, coming to rest on the overly-sensitive mound above her slit. Gingerly, she rubbed at it. The slightest touch was enough to send burning pleasure arcing through her body.
Nightmare Moon hit her peak as Luna was coming down from hers, sending a violent aftershock of pleasure through Luna. More droplets spattered the ceiling of Luna's alcove, but she didn't notice. Eyes closed, she was enjoying her post-orgasm glow, this time in the safety of her makeshift home. Subconsciously, she slipped her fingers inside her vagina, soaking them in liquid, and slowly slid them into her mouth. The sweet taste was strange, but it was one that Luna found that she enjoyed. She rubbed her lubricated fingers over her nipples, feeling them harden once more, sending waves of dull energy through her.
She fell asleep, more content than she'd felt in years.
This continued for every night afterwards. Every day was a little more bearable, knowing that her night would be warmed by her friend and lover.
Day by day, however, Nightmare Moon became more and more restless.
She spoke of prophecies, and glorious vengeance. It scared Luna. Every night, Nightmare Moon became more and more forceful in her using Luna for pleasure. Some nights she even hurt Luna, but she always apologized.
One night, when the time came, Nightmare Moon was even more angry and aggressive than usual. She took out her anger on Luna, increasing the quantity of energy she used to pleasure herself, pounding in and out of Luna's cunt. Even after Luna climaxed, Nightmare Moon commanded her to get on her knees, and took her again. Midway through, as Luna's orgasm was building once more, the energy was removed from her vagina and roughly inserted into her ass. Luna opened her mouth in a silent scream, her eyes filling with tears. It pounded her again and again. Luna gritted her teeth and tried to endure the pain, trying to comprehend what kind of sadistic pleasure Nightmare Moon could be getting from this. She could hear her other side screaming inside her head, but hers were screams of ecstasy, commanding herself to go harder. When she orgasmed, it was all Nightmare Moon. It was a horrible, brutal feeling. She could feel liquid squirting and running down her legs, though from which orifice, she could not say.
The energy dissipated, and Luna collapsed forward, in tears. She heard Nightmare moon sigh contently.
She lay in her alcove, shivering and crying. She felt betrayed, and used. Worst of all, for the first time in years, she felt completely and utterly alone.
The next day, Nightmare Moon took full control. It came, sudden and forceful as a hurricane: agonizing pain, as Nightmare Moon took control of Luna's body. It was over as soon as it began. Soon, Luna was the voice in the back of Nightmare Moon's mind, albeit a feeble one. Every time Luna tried to plead with her other half, she was ignored. Nightmare Moon closed her eyes and raised her arms, and a vale of dark energy surrounded her, wrapping around her like a dark shroud. When it dissipated, Nightmare Moon was clothed in a beautifully savage dress of midnight-blue silk, inlaid with sapphires and bits of onyx. An onyx and silver crown rested on her head.
Come, my dear, Luna heard, the voice like thunder. We're going home.