When the Sun Princess of Equestria woke up to commence with the crack of dawn, raising the sun to spread its exuberant rays, her mood was anything but pleasant. First of all, she felt utterly exhausted, as though she had been sleepwalking for hours and doing strenuous activity rather than calmly resting in her bed. Additionally, for some entirely unknown reason, her head was pounding with a fierce migraine, the likes of which was devastating. The last time she had felt such significant pain was when she was shot down by Chrysalis, the Changeling Queen, and even that was more of a brief, temporary damage.
This, however, this was practically debilitating, and never seemed to end. Every minor light was a million suns burning out her corneas and vaporizing her irises. Every squeak, crack, and subtle noise was a cacophonous roar of gongs, cymbals, and combustion. Still sleeping in her royal bed, however, Princess Celestia knew she must find a way to trudge through her pain, displaying only calm, serene confidence. For such was the lot of a ruler, to be for the ponies what was needed for the ponies. She had to be strong, but the pain was unbearable. What could possibly be causing such pain?
Regardless, Celestia had her duties to attend to, and they could not be excused no matter how much she was suffering.
Walking out to the Royal Balcony, her hoof steps echoing as loudly as if the universe desired only to destroy her eardrums, Princess Celestia gazed out at the horizon with concentration. A warm golden glow enveloped her horn, though even the mere act of concentrating on a single task sent stakes of pain jabbing through her brain. Gritting her teeth and bearing it as best she could, she set the sun to rise from the horizon, and started the day off on its way. But never before had she had such difficulty in performing what was by now one of the spells that she was most familiar with, most comfortable with, most capable with. What was causing this disaster of a headache, and why did it have to be her?
While rubbing her hooves into her temples and a pointless attempt to alleviate some of the pain, Princess Celestia spotted a letter out of the corner of her eye. Assuming it was some sudden letter from Twilight which had somehow escaped her notice, she walked over to her bed where it was lying unassumingly on one of the many pillows. Yet something was a bit off about this letter. It was in neither Spike's nor Twilight Sparkle's hoofwriting. Was it...her hoofwriting? What?!
She snatched up the letter with her warm golden glow of levitation magic and quickly scanned the contents, her face morphing into a visage of shock and distress.
"Good morning, Princess Celestia. Or should I say, myself? Hahaha, guess what? You're possessed! And whenever you go to sleep, I can control your body. That's probably why you feel so poorly right now. I used your sleeping body to write this note. What will I do next? Luckily for you, your subconscious mind is strong enough to keep me at bay while you're awake, but eventually your defenses will fall. And I will take over your body, holding you prisoner in your own mind. So the next time you rest your head upon this pillow...think of me, and wish for happy dreams!"
She noticed some indecipherable scribbles at the top, along with a few small drops of saliva and ink on the page, as if she was just learning to use her mouth to write, and getting the hang of things before launching into the message. At the end of the note, it seemed as though she saw the beginnings of a smiley face, but it transformed into a grimace as though the quill had been wrenched off of the paper at the last minute.
Overcome with disbelief, she re-read the message again and again, trying to make sense of it all, but she just couldn't. Eventually she decided on chalking it up to an overactive imagination. Maybe this was just her mind playing a trick on her, through somnambulism brought on by stress. And could this be in any way related to that strange sneeze from earlier? No, that didn't make any sense. Nothing made any sense! It was as though all logic had suddenly been cast away from the world, replacing it with something even more bewildering. This couldn't be happening.
Was it Discord up to no good again? No, that was impossible. He was imprisoned by the Elements of Harmony. And so was the evil maleficence of Nightmare Moon removed from her younger sister, Luna. Or was there a weakness to the Elements? Whatever was going on, it signaled only pending trouble. She didn't like to admit it, but she needed help. So she decided to take this problem to her sister, Luna. If anyone would understand her, it was her little immortal alicorn sister.
"Oh, hello, sister. Is something wrong?" asked the tired Luna. Being essentially nocturnal, she was usually sleeping during the day, and always a bit slow to wake up. A little bit groggy, a little bit angry, a little bit short-fused. But still kind, throughout it all. Celestia had just woken her up, gently as possible, but nopony could say that Luna was a morning person. This was a task to be handled with delicacy.
"Sorry to have woken you up Luna, but there's a matter of pressing importance which I must discuss with you. But before we start, would you like a cup of coffee? I made a cup for you, black as night and sweet as pie, just the way you like it."
The Sun Princess levitated a simple mug over to her sister, who accepted it gratefully, but with a hint of suspicion. Much as Luna enjoyed getting her morning coffee in bed, as she always needed whenever up and about during the daytime, normally she had servants fetch it for her. Why did her sister Celestia bring it this time? Yet she put her worries aside and enjoyed gulping down the rich blend, almost but not quite burning her tongue as the scalding brew invigorated her.
"Mmmm...thank you for the coffee, you're a goddess if ever there was one," replied Luna gratefully, a hint of a smirk gracing her features. "But what is the occassion? And why did you see fit to awaken me from my slumber?"
"Well...it's just something that I have to tell you about, and I don't think it can wait. I'm sorry to have cut into your dreaming hours, but I would greatly appreciate it if you'd just hear me out."
Luna seemed slightly surprised at the request. "Of course, Tia! I'm your sister. I couldn't possibly withhold assistance from you. I know we may have had our differences, but you should know by now that you can trust me with anything." She finished her statement by looking her elder sister straight in the eyes, attempting to convey as much sincerity and fortitude in that gaze as she could possibly muster.
Reassured, Celestia nodded and decided to reveal to her sister what was going on. "Well, realize that this is tough for me to say, but something is seriously wrong. I think my mind is playing tricks on me. At least, I hope that's what is happening. Otherwise, things might be far more serious than I fear. As it is, I found a note on my pillow today, in my own hoofwriting, and I think you should read it." She floated the letter over to her sister, grimacing at it in distaste for what it meant, what it represented.
Luna took it with her own magic and quickly analyzed the words. They indeed seemed to be in Celestia's hoofwriting, but somehow more...flawed. But as she continued reading, the seriousness of the matter at hand thrust all trivial details such as that aside in her mind. "But...this...this is...but..how can it be? What's going on? I just don't understand! We have to do something, but I don't know what to do! Should we find some way to monitor you during your sleep? Strap you down in bed? Oh, what to do, what to do!" When Luna finished her speech, which was loud but not ridiculously so, Celestia's migraine struck again in full force.
Celestia groaned pressed a hoof to her forehead, closing her eyes in pain as a grimace crossed her face. "Please...speak a little quieter. I have a terrible headache which causes extreme sensitivity to sights and sounds," she murmured in a near whisper. "But you're right, we have to do something. For now, I don't think we should resort to too extreme of measures. I have an idea, though."
"And what would that idea be?" queried Luna, eager to help her sister in her time of need.
"Well," Celestia responded, "perhaps we should rely on your skewed sleep schedule. When I need to sleep, I'll ask you to come to my room and watch over me. If I seem to awaken, or act strangely, you'll be there and hopefully you'll figure out what's going on. I know that I needn't tell you the crucial importance of this matter. We're not at all sure what we're dealing with, so you'd do best to exercise extreme caution. We want to understand the possible creature in my mind, so please try all you can to reason with it, help it calm down. Because I think it may be what's causing this migraine, and I'd like to make that stop, if possible."
The Moon Princess nodded in understanding. "I shall watch over your sleeping form with vigilance. Please try and rest easy, if possible. I promise you... I will protect you."
"Thank you, Luna. You're a good sister, and I love you," Celestia said, embracing her sister softly.
The younger alicorn returned the embrace and replied "Love you too, Tia."