"Are you fully prepared, sister?" queried the Sun Princess of her younger sibling, eyeing her warily from her palatial bed.
"As I'll ever be, Tia," the Moon Princess responded, a look of confident calm displayed on her face.
"Well then... good luck, and good night, I suppose. I shall expect a report when I awaken as myself," Celestia finished, shuffling and shifting a bit to try and find the perfect position for peaceful sleep.
"I know, big sis. Like I said earlier, thou can trust me with anything," Luna continued, a gentle smile upon her visage. "Anything at all."
A few hours had passed by, given willingly to the all-consuming night, but so far Luna had detected no change in the behavior of her big sister. Her nightly vigil began to seem a lot more boring than she had anticipated, but it was quite peaceful. Although being banished to the moon for a thousand years had caused her to consider being alone in an entirely different light, right now it was actually... somewhat pleasant. Celestia's bedchambers were currently pervaded by a pleasant kind of silence.
After all, there were many different kinds of silences. The silence of the night was common enough. Though sometimes punctuated with an interesting breeze or two, it was the kind of silence which laid over the land like a warm, comforting blanket, only accentuating the half-hearted attempts that some might make to dissipate it. Then, there was the silence of frustration. A silence when you desired, to the point of anger, a disruption, but nothing you can do combats it. A silence so loud that it practically yells at you, taunting you, trying to get a rise out of you. Definitely not a silence she preferred. No, this pleasant kind of silence, it was the restful period after the others had gone to sleep. A respite from the hustle and bustle of everyday activities. The kind of silence in which subtle inspiration can be born. The kind of silence in which you can take a moment to admire the world around you, and marvel at its intricacies, without your thoughts descending into a jumbled entanglement.
Yet despite being pleasant, even a comfortable kind of silence can generate ennui after a long enough period of time. It would be great if Tia wasn't possessed at all, but Luna couldn't help the fact that staying up all night looking at a sleeping body was a bit more interesting if said body was actually responding to outside stimuli.
Still, she did have an adorable sleeping face. And it was interesting to see her face actually calm, her breathing deep and measured, simply relaxed. She was almost like a different pony when asleep. No longer the wise, stoic ruler, she even snored a bit, and might have let just the tiniest bit of drool escape from her otherwise-immutable control. Luna gently wiped that off of her sister's face with tender, sisterly affection, and then jolted in surprise when suddenly her sister's calm, resting demeanor evaporated. Her sister's eyes flicked open, but within their depths Luna did not find the kind, loving patience of Princess Celestia. Rather, it seemed that Celestia's face bore a look of surprise, as if she had never before seen Luna in person.
With a gasp, the formerly sleeping alicorn exclaimed "Whoa! Princess Luna, in the flesh!" An almost sinister smile seemed to spread across her normally gentle features, and she continued "You know, I think I've always liked you more than your sister. I'm not entirely sure why, though. Sure Celestia's nice but Luna...I mean you...you're just kind of more cool, y'know? Heheh."
Baffled, Luna decided to try and rely on her sister's instructions, which generally boiled down to "Please stay nice with the malevolent spirit currently possessing my body". Awkwardly, Luna tried to dredge up an amicable smile, but it far more closely resembled a grimace. "We...we are pleased to meet thee, kind spirit. Dost...thou have a name with which thee refer to thyself?"
Only chuckling more, the unknown entity responded with a smirk. "Oh, you didn't get my letter? What a shame. The name's John Doe. Pleased to meet your acquaintance, Princess of the Moon. But gosh, you're just so darn cute when you're flustered! Quick, say something else.
Now more baffled than ever, Luna had no idea what to say. "Art thou saying that you...likest me to speak to you?"
And giggling like a filly, not-Celestia only replied "See? That right there. The formal speech, the slight awkwardness in meeting someone new... it's just so... D'awwwww! But uh...ahem... Oh! I know! Let's have a cup of tea! You like tea, right?"
Unsure of herself, the dark blue alicorn only nodded slowly.
"Excellent! Where's the kitchen? What kinds of tea do we have at our disposal? Do you like yours with milk and sugar? Or maybe honey? Wait a minute... why were you watching me... I mean us... sleep?" responded the possessed Celestia, the subject of hot beverages vanishing from the possessed mind like a feather before an infernal incinerator, as curiosity warped into suspicion.
Realizing that she would only make John Doe more suspicious were she to lie, she decided to wing it and simply tell the truth. "I'm merely observing my elder sister's sleep to safeguard against any anomalies. And as... pleasant... as it is to converse with you, you are most certainly not Tia, and therefore are most definitely an anomaly."
"An anomaly, huh? Why, you make it sound as though I'm the bad guy! That's just not nice at all."
With that ludicrous response, Luna's scorn began to rise at this... ridiculous being residing in her sister. Her temper, though normally slow to ignite, flared up instantaneously, and the Princess of the Moon threw caution to the wind.
"What business have thee to declare me unpleasant, after what you have done, so infesting my sister's mind? How dare thee invade her so thoroughly as to disturb her otherwise peaceful slumber? And how dare thee pretend to feel so comfortable within her skin, after causing her so much pain? If I could safely do so, I would not even banish thee to the moon. I would tear thine essence from my sister as desperately as an Ursa Major protecting her cub. And before washing my hands until these hooves were raw, to get the filth of your existence off of them, I would thrust you so far into the vacuum of space that thy spirit would never be found, doomed forever to float in desolate loneliness and to contemplate only suicide!" With a huff, Luna did feel better after her outburst.
But only too late did she realize what a mistake she had made. By inviting this demon's displeasure, she would almost certainly guarantee her sister a world of pain when she awoke. Suddenly unsure of herself, Luna could only tear her gaze away from her not-sister, fearful of what would happen next. Would Tia's reward in entrusting her safety to her younger sister only result in more horribly painful migraines? Would Tia ever trust her again? Self-doubt upon self-doubt weighed heavily upon the relatively young alicorn's psyche, inducing a pain not of the body, but of the mind and spirit. Still, after saying so much, she could hardly retract her statements. She meant every biting word of her monologue and retained her anger, but by now it had become far less potent than before, tempered by uncertainty.
"Please," Luna now demanded with only the semblance of politeness upon her scowling face, "Leave my sister. Return to the accursed place from whence you came."
Now bearing what was definitely an evil grin, the Celestia impostor only seemed wickedly delighted at her outburst, as if it had given him license to torture Celestia however he pleased.
"My my, quite a temper we've got on us, haven't we?" smirked John Doe. "Just so you know, I couldn't return to my world even if I wanted to. I haven't the faintest idea how I got here, other than that it was somehow related to a sneeze. Before you get any ideas, I can assure you that putting spices up your sister's nose to induce one will only cause her unnecessary respiratory distress. It won't send me back; trust me, I've tried. But rest assured, your sister will pay for your outburst. I will take her over after she raises the sun tomorrow. That's a task which I'm sure will remain within her hooves for the time being, as I do not care to destroy this world through my incompetence. Still, I will take control of her. I will subjugate her will to mine. I will become more powerful than any other pony. And even if I don't succeed in leading this body, I will wear your sister down until her defenses crumble like so much gossamer and morning dew. Until I get my way, her life shall be a living hell, consequences be damned. And she'll have only you to thank, my little alicorn princess. For your rude words, the only one to suffer will be your dear, sweet sister Celestia."
Now unable to even muster up even the tiniest hint of decency to John Doe, Luna could only spit out her frustration in two carefully chosen words, dripping with as much malice as she could conjure. "You...monster!"
Responding with feigned affront, Celestia's warped visage only replied with further spite. "Perhaps. But as long as I'm here, your words can hardly hurt me. The only way to get rid of me right now would be to get rid of Celestia. Oh, the delightful tragedy! I, despite my position of tenuous power, am still leagues ahead of you in leverage. Within my hands, as control over you, I hold your sister's life. All you have to throw at me are words which can only worsen the situation. Ponder that until my next return, Luna." After finishing with his soliloquizing, John Doe walked Celestia's body back to the bed and laid upon it. Before leaving, though, he turned Celestia's face towards Luna and muttered in as insulting a voice he could muster, only two words. Two very haunting words. "Sweet dreams." Celestia returned to her slumber, but rather than a look of calm, she wore an expression of pain and torment.
Now weeping in terror, in fear, in sadness, and in angst, Luna could only question herself.
"What have I done?"