It’s a quiet night as Luna glides gently over Canterlot. She breathes deeply of the cool night air and surveys the buildings below her. Everything glows softly in the moonlight, and she smiles at her work.
Few are awake to appreciate the sight aside from herself, but that’s alright. She has decided she doesn't mind the ponies sleeping through her night as much as she once did. So long as she has her sister, and can be back in Equestria where she belongs, she’ll be happy.
The princess of the night alights gracefully on the roof of one of Canterlot Castle’s high towers. She closes her eyes to listen to the sounds of night. The cool night breeze whistles near imperceptibly past her ears. An owl hoots quietly in the distance. She notices a series of clattering noises nearer by. Looking to the source, she sees a small light still on in one of the homes below. A pony who had clearly been working late was attempting to get his things in order so that he could go to bed.
She smiles and looks to the sky. She’s glad to be able to enjoy this pleasant night. Everything has seemed so much more wonderful since she got back. She supposes it’s the novelty of it, after being away for so long. Everything felt brand new to her, and some of it truly was. So many new discoveries and changes in society. Equestria had changed so much in a thousand years.
Nothing has truly changed though. You know this.
Luna’s veins turn to ice, her heart nearly stopping. She’s certain she’s forgotten how to breathe.
“Get out.” Her voice is barely a whisper. “Get out of my head, you foul demon.”
I am simply stating a fact. What has changed in the time you’ve been gone? These ponies still shun your night. If anything, they hate you more after what you did.
“After what you made me do!”
As if there is a difference.
“There is a vast difference. Had I been in control of myself, I never would have-”
Do not forget you are the one who let me in. You wanted my power. Don't try to push blame, little Luna.
Luna closes her eyes and attempts to calm her panicked breathing. She does not need this monster to remind her of her unending guilt. She is more than capable of reminding herself. “Regardless, it is not something I will ever do again. So leave.”
Oh, really now? Never again? Ha! All that had concerned you before is still here. They still sleep through your night. They still ignore your existence unless it is convenient for them. They still love your sister more than they shall ever love you. It is only a matter of time before you are begging for me to help you once more.
“No! You are wrong. Things are different now. I have friends. I have the love of my sister. She tells me every day how greatly she appreciates me.”
A lie, meant to placate you so you do not rebel again.
“Stop it! My sister has never lied to me! But lying is all you have ever done.”
I speak the purest truth. The kind you dare not even think to yourself. Just because you are more comfortable believing a convenient lie, does not put me at fault for speaking true.
“Shut up! GET OUT OF MY HEAD!” In a desperate attempt to flee, Luna launches off the rooftop and flies as quickly as she can. The voice laughs.
You cannot outrun me, little fool. I am a part of you.
She has to make it stop. She has to get away. The frantic alicorn drops into the nearest open window of the castle and runs down the halls as quickly as she can.
Ah, poor little Luna. As lonely and fearful as ever. You know I can help you.
She ignores it and continues to run, skidding around corners and scrambling up stairs, ignoring the guards who stare at her as she passes.
Where is it you think you're going?
She doesn’t answer, as she sees her goal ahead. The pair of guards at the entrance stare at her in confusion as she approaches at lightning speeds. She can see the hesitance on their faces as they try to figure out whether or not they should stop her. She ignores them as well and bolts through the double doors shouting.
“Tia!”
Her sister starts awake as she leaps onto her bed.
“Sister, please wake up, I need your help!” There are tears in Luna’s eyes, and her voice has reached a frantically high pitch.
“Luna, what is it? What’s wrong?” Celestia is fully awake in an instant at the sight of her terrified sister. She places a gentle hoof on her shoulder in an attempt to calm her.
“She is in my head, Tia. She is in my head and she won't stop. Spreading poisonous thoughts, trying to take me again. Sister, please, make her stop!”
You truly run to her for help? She who caused you such hate and resentment in the first place.
“What do you mean, Luna? Who’s in your head?”
“Nightmare Moon!” The tears are running freely down Luna’s face now while she stares pleadingly at her elder sister for help.
Celestia’s eyes widen, and for a moment, she looks as frightened as her sister. Then she steels her gaze, pulls Luna into an embrace with her forelegs, and spreads her wings over her protectively. “It’s alright, I'm here now. I’m here, and I won't let her take you.”
“I’m scared, sister.” Luna’s tears fall quickly onto Celestia’s white coat. “She speaks poisonous words into my mind. Tells me I am hated.”
“No one hates you, Luna. Don't ever think that.”
“I know! I know she tells only lies. That is what she does. Spreads treacherous lies, until I can no longer see the truth behind the false world she has created. I know it is so, but still I…”
You still see truth in my words.
“Stop it!” Luna presses her hooves to either side of her head, trying to block out the voice. “I am so frightened, Tia. I don't want to be prisoner within my own mind again.”
“You won’t be. You're stronger than her, Luna.”
“I wasn't before. I was a weak, insecure, fool. I let her in, and she did terrible things.”
“You were sad and lonely. Such actions are understandable when those feelings are preyed upon.” There's a pause before Celestia is able to continue. She swallows heavily and takes a steadying breath. “And I was neglectful. Had I been paying attention, I would have seen what was wrong. I could have eased your fears. What happened was as much my mistake as it was yours.” The elder alicorn lifts her crying sister's head to meet her eyes. “But it is a mistake I will never make again. I am here for you now, and I will not let anything happen to you. I'll be here for you as long as you need me.”
Luna offers a weak smile. “Thank you.”
The voice growls.
Cowardly little foal. Running to big sister to protect you. You are more pathetic than I had given you credit for.
The shivering night princess whimpers, and buries her face in her sister’s chest fur.
Celestia tightens her hold on her frightened sibling, trying to help her any way she can. She looks up, and realizes her two guards had been watching them since Luna had burst the doors open. They jump at having been caught staring. The princess of the sun glares at them, and they quickly close the doors again.
She resumes comforting her sister, running a hoof over her mane and whispering soothing words. She recalls lullabies from their foalhood and sings them softly in attempt to calm her. When the Nightmare’s voice becomes especially aggressive, Luna sings along tremulously, wiling herself to concentrate on anything but her lies.
It is hours later when the voice finally seems to have given up. Celestia looks out to her balcony. “Time for sunrise,” She says quietly.
Luna pulls away, “I'm sorry. I've kept you up all night. Let me-”
Celestia shushes her and gestures for her to lay back down. “It’s fine. You stay right where you are. I can do it from here.”
Luna hesitantly goes back to where she was and watches as her sister effortlessly pulls the sun into position. “You took care of removing the moon and stars as well,” she comments softly.
“I didn't want you to worry yourself.”
Luna gives a wry smile. “I thought half the point of my being back was to ease your burden after a thousand years of doing my job.”
“The point of your being back, dearest sister, is that the two of us are reunited.” Celestia rubs noses with her in a show of affection.
Luna laughs, remembering when they were fillies and she would frequently use this gesture to calm her.
“But, I suppose you have a point,” the elder alicorn goes on. “You can do sunset for me later.”
The smaller princess smiles and nods. “An acceptable compromise.”
“Sleep now. You've had a long night.”
The younger alicorn does as she’s told and rests her head, feeling tired instantly. She opens her eyes again and mumbles, “Tia?”
“Yes, little sister?”
“Thank you, for being here for me.”
“Always, Luna.”
It doesn't take long before the exhausted mare is sound asleep. Her sister smiles, then retrieves a quill and parchment with her magic to write a note for her personal assistant.
Please move all of my meetings for the day to another date. I need to be with my sister today.
-Celestia
She rolls up the scroll and sends it to her assistant with a burst of magic. A few Canterlot nobles would be inconvenienced by her absence for the day, but they would simply have to deal with that. Some things were more important.
Celestia settles down to sleep as well, cherishing the warm presence of her sister safely by her side. Everything will be fine, so long as they have each other.