From her perch at the edge of the tallest tower, Celestia gazed over the walls of Canterlot Castle as she lowered the sun for the day. Staring intensely, she focused all her attention upon her final daily duty. In fact, such single-mindedness was unnecessary now. When she had been younger, the activity had taken all her concentration; but after so many centuries, she could now lower the sun while barely paying it any mind (and had, on several occasions). The intense focus was for her sake, rather than the sunset's. It was a convenient way to clear her mind after the sometimes-frantic business of the day. She appreciated the opportunity for a few moments of calm, in which she contemplated nothing but the immediate task at hand. As the last edge of the orb dipped below the horizon, she let out a peaceful sigh, and basked in the gentle light of the dusk, knowing that behind her, Luna's moon had just fully emerged.
A voice like a funeral bell rang behind her.
"Hello, Celestia."
Her breath froze. No. No.
She spun around.
Pitch-black had replaced Luna's normal deep blue coloration. Her mane remained as normal, but framed a face Celestia couldn't mistake, staring at her with scorn. And those eyes...those horrible slits of malice.
Nightmare Moon smirked. "You look surprised."
"Luna...no, I-"
Without her battle-helm, Luna's distorted features were clearly recognizeable. It was grotesque, like someone had taken her younger sister and twisted her into some not-quite-right version of herself.
"You thought I was reformed? That I would just forgive you after what you did to me? That being hit in the face with some kind of ridiculous rainbow would make me just forget everything?" She chuckled. "You pathetic foal. Did you really believe I would come back and be your shadow again, just like that?"
Nightmare Moon's voice suddenly changed timber. "I'm so sorry. I missed you so much, big sister." It was Luna's voice, but twisted into a biting mockery of her sister's words.
"I must admit, I expected to die there," said the voice of Nightmare Moon. "Imagine my surprise, when instead of putting me out of my misery, you knelt down and offered me 'your friendship', just like nothing had happened."
She cackled with callous mirth.
"Oh, at first I thought it was a bad joke. But no, you were serious! You must have become even more credulous over the centuries. How you managed to stay in power so long with that kind of stupidity, I have to wonder. But it was quite fortunate for me. It gave me time to recover before getting rid of you for good. And to eliminate the threat of the Elements."
The Elements.
"How did you get through the vault?"
"I didn't. I didn't have to. The Elements are safe and sound, for all the good they'll do you now. No, I didn't need to get to them to handle that particular problem."
Luna hurled something from behind her wing. Celestia forged her magic into a shield and braced herself, expecting an attack. To her surprise, the item bounced off harmlessly and clattered forward onto the cobblestones.
It was a purple horn.
Celestia stared, trying frantically to stop her mind from understanding what she was seeing. The bottom of the horn was red with old blood. A few stained purple and pink hairs had formed clusters, grouped together where the blood had dried. A fragment of skull was still attached to the base. Its edges were jagged and rough -- the horn hadn't been cut off. Celestia's stomach lurched.
"I must say, you did an abysmal job of teaching her. She could hardly put up a fight at all. I could take all the time I wanted with her. She must have made a very poor replacement." Hate and anger twisted the last word into a growl. "But then, I suppose we work with what we can find, don't we?" The words seethed with bitterness.
A sob welled in Celestia's chest. She forced it down, and raised her head to look at the thing that had been her sister. She didn't know how many others -- no, how many; it was a lie, it had to be -- Nightmare Moon had killed. Hopefully she could stop her before she killed any.
"Oh, finally ready to fight, are we? No more slinking around playing chessmaster? No more entreaties to my better side, to 'end this madness'? No more 'I know you are still there, Luna'?"
Pushing down her fear and sorrow, Celestia eyed Nightmare Moon levelly. "No."
Nightmare Moon raised her eyebrows at that. "Well, I guess even you get it eventually. Now, die."
Purple energy flared and shot from Nightmare Moon's horn, striking exactly where Celestia had been as she leaped to the right. A series of identical bolts followed, forcing her to continue to gallop in a wide arc as she sought an opening in the other alicorn's defense. Nightmare Moon suddenly broke off the volley, and charged her.
Celestia forced herself to a halt and spun to face her attacker before Nightmare Moon could strike her exposed side, but she now lacked the solid footing she needed to stop her sister's charge. Frantically backpedaling, she rapidly shifted her horn to deflect a stab that the other alicorn aimed at her eyes. With no loss in momentum, Nightmare Moon followed the attack up with a series of several more quick darts, trying to blind her. She deflected each one in turn, but they kept coming. Celestia couldn't establish a steady stance from which to fight.
A strong blow to Celestia's chest knocked the breath from her, sending her rolling to the stone floor and crashing against the parapet. She'd been too focused on defending her face, and the other unicorn had taken advantage of the distraction and kicked her in the chest with her forehoof. Gasping for air, Celestia rolled to the side, leaping to her feet just in time to block another horn-strike at her face.
Nighmare Moon shoved her head forward, hoping to overpower Celestia, but the elder alicorn now had regained her footing, and the two shoved to a standstill, horns locked. Celestia quickly shifted her horn to the side and pushed her head past Nightmare Moon's. At the same time, she stepped forward, locking her front knee with her sister's, and shoved her weight forward, unbalancing her opponent. Thrown off balance, Nightmare Moon was unable to defend herself, as Celestia spun on her front hooves and threw a full-force buck into her sister's face. Knocked senseless, the younger alicorn sprawled on the floor.
Celestia turned and used the few seconds she'd bought herself to summon a bolt of her own. But just before she could release it at her opponent's still-receding form, her sister disappeared in a flash of indigo. Celestia focused and willed herself to hold the spell, confining the energy to her horn. Eyes darting around the tower-top, Celestia frantically tried to find the destination of the teleportation spell. The briefest shimmer of indigo a score of strides to her left gave her the answer, and she spun to face the area just as Nighmare Moon materialized in another flash.
Shrieking in rage, the ebony alicorn charged her down. Lowering her horn, Celestia released the golden bolt. Nightmare Moon's indigo shield flared, strained...and the bolt passed through, striking the other mare in the face. Her head snapped backward, but she recovered and shook it off, raising her eyes to see where Celestia had moved. The bolt had barely slowed her forward momentum.
It didn't need to.
Celestia shifted her horn half a foot, under Nightmare Moon's raised chin, and braced herself against the impact as she impaled the other alicorn through the neck.
The slam of the impact shoved her backward. The charge stopped. Blood sprayed from Nightmare Moon's wound in the sudden silence. The black alicorn collapsed, dragging Celestia with her before she could withdraw her horn. On the ground, she struggled to free herself as the crimson stained her coat.
"Tia?" Celestia froze. She must have missed her larynx. The voice was weak, but clear. And it was Luna's.
"I hate you."
The last of her sister's weight dropped onto Celestia's neck as the life left her. Celestia didn't care enough to fight it, letting herself roll to the ground with the weight, coming to rest with a dull thud. She lay there for several seconds, trying to keep from thinking, from understanding, for as long as she could. A sharp pain arose in her throat, and her eyes began to well.
Making no attempt to rise, with her sister's corpse upon her horn, Celestia cried. Tears mingled with Luna's blood streamed down her face. Clenching her eyes against the stinging liquid, Celestia could only sob. Luna was dead. Twilight was...Twilight was dead, she admitted, as the vise clenching her chest tightened. There was no way Luna would have acted if the Elements had still been useable.
Luna had been right. She hadn't prepared Twilight. She hadn't protected her. She had wanted so badly to believe in her sister's reformation that she had risked the lives of all her subjects. She had failed them all. And now both her sister and her protegé -- the closest thing she had to a daughter -- were gone. Amid the sobs, a wail of grief burst from her throat, and she fed it until she had no breath remaining.
Galloping hoofbeats sounded from the stairs below, approaching her. The guards had heard the fight. Let them find her there, like this. Celestia could not care anymore. She could not care about anything.
The stomp of a hoof sounded by her head, and her sister's weight disappeared from her neck. Celestia opened her eyes to look up, and immediately clenched them shut again as they burned with blood. She had seen...no, that was impossible, she was seeing things in her grief. She wiped the red from her eyes. One of Luna's guards must have found her. She would have to explain.
"Tia?"
Her gaze snapped up. Her eyes stung, but she hardly noticed.
Luna.
She must be hallucinating. Perhaps she had gone mad with grief, she thought in the back of her mind. She glanced over to Nightmare Moon's corpse. It had vanished.
Her sister -- the image of her sister -- fixed her with a look of anguish and concern. "Oh no, I...I am so sorry Tia. I came as soon as I heard you."
"How..." Celestia could barely form a sentence.
"Shhh, it's okay. Everything's okay." Luna reached her head down. Celestia recoiled, afraid of feeling nothing, but Luna's face was solid and warm against hers. "She's gone. She's not coming back. I promise."
Celestia looked up into her sister's face, still not comprehending.
"It's no more than a bad dream."
_______________________________________________
Celestia awoke with a start. She was gasping for breath. Her heart was racing. Her stomach was a knot.
She looked around. Her bedroom. The sheets and pillow were soaked with sweat, but otherwise, everything was normal. With a sigh of relief, she collapsed back onto the bed, breathing deeply, trying to quiet her pounding heart and ease the ache in her chest.
Luna. She should check on her, she thought, rising. Just...just to be sure. She wasn't going to be able to sleep anytime soon, anyway. She may as well keep her sister company. As she crossed the room to the basin to wash herself, a knock sounded at the door.
"Tia?" her sister's concerned voice sounded from outside. What? Had she heard her? "Are you alright?"
Oh, of course she knew, Celestia berated herself, finally realizing.
"I'm...I'm fine, Luna." Her voice was less stable than she preferred. "Just a moment." She reached the basin and washed away the worst of the sweat and tears, then floated over a towel and dried herself. Straightening her mane to a slightly less disheveled position, she called, "Come in."
The door floated open and Luna entered, looking like her sister again. She nodded to the guards outside as they shut the door behind her, then quickly trotted over to Celestia. Before Celestia could say anything, her sister had wrapped her in a tight hug.
"She's gone, Tia. She's gone. She's never coming back."
"I know, I know," Celestia said, returning the hug. They stayed that way for a few moments. "Thank you, Luna. I'm glad I didn't have to spend any more time there."
Luna released her. "I should have arrived sooner, I'm sorry. I didn't realize what was happening. I was checking on the Timberwolf migration and-"
"You were busy doing your duty. That is more important." Celestia smiled slightly.
Luna eyed Celestia with annoyance. "No, it isn't.
Celestia was in no mood to argue over something so minor, so she let the matter drop.
"Anyway, I should be fine now," she said with far more confidence than she felt. "I should get back to bed."
Luna glanced at her askew. "You never go back to sleep after a nightmare. You haven't since we were foals."
Blast. "I'll be fine. I'll occupy myself with something. You need to get back to your duties."
"Everyone's dreams are peaceful tonight -- besides yours. And I'm finished with everything else urgent. I was taking care of things that don't need to be done for a month."
Now it was Celestia's turn to look skeptical.
"Tia, why would I lie to you? You always catch me when I do."
That was actually true, and Luna seemed to be honest.
"All right. Come on. I was going to sit outside for a bit."
Looking rather satisfied with herself, Luna followed her out onto the balcony.
The night was cool, but not chilly, and was pleasant after the stifling bed. Celestia gazed over the murky courtyards, knowing that Luna could see them as though it was broad daylight.
"Is anything interesting happening that I can't see?" She'd been asking Luna that question for as long as she could remember.
Luna gazed downward. "Lady Ermine's colt is sneaking around the bushes. I think he's trying to climb the statue of Starswirl again."
Celestia chuckled. The young pegasus was a late-blooming flyer, and had decided to try climbing in the meantime. Groundskeeper Greengrass had been trying to keep the boy away from the castle statues and towers, with very little success.
They sat in the quiet night air for several moments. Then Celestia asked something she'd wondered since her sister's return.
"Luna?"
"Yes?"
"Do you ever have nightmares about...then?"
Her sister glanced at her for a few seconds, then nodded. "Sometimes. Usually they're just memories. But...sometimes they become...difficult."
Celestia winced inwardly. Her sister was the only pony in Equestria who had no one to wake her from a truly terrible dream. She hoped Luna rarely suffered ones as bad as her recent one.
Luna continued, gazing down at the courtyard again. "I never told you how it happened, did I? Why I did it? I mean, I know I told you in general, but I haven't really told you the story, have I?"
Celestia paused. "No. I decided you would tell me when you were ready, and I didn't want to make you dwell on it any more than you had to."
Luna shifted her gaze from the courtyard to Celestia. "Would you like to hear it now?"
Celestia nodded. "If you think you're ready to tell me."
Luna took a deep breath, then let it out with a sigh. "All right."
"It started a few months beforehand..."