The...Nightmare?
Twilight was jolted from her mind conversation by a bright glare coming from the corner of her eye. Turning her head slightly, making sure not to blind herself, she saw with shock that it was coming from the two alicorn's horns.
A spell.
Twilight began to shake. Had the voice been right? Was Celestia going to kill her?
The glare got brighter, growing in power.
She wouldn't. Just because she was hearing a voice? How did her mentor even know?! Was she just going to kill her for the fun of it, and the Nightmare, whatever it was, was just trying to calm her down..?
Teleport! Now! I'll explain all of this later. The voice had been drained of all it's humor - now it was full of a fear that sent a chill down Twilight's spine.
Suddenly, a bright flash filled the room, consuming the purple glow that suddenly winked out.
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The flash faded, and Luna let her power go. She steadied herself, weakness threatening to consume her, and she evaluated the area.
Everything seemed to glow from the after affects of the cleansing spell, chasing away any darkness that may have lurked in the room. It was one of the most powerful spells known to ponykind, needing the power of two alicorns to perform it - and even then, it was incredibly draining.
Luna gasped. She weakly rubbed at her eyes with a hoof. Had they been too powerful, destroying Twilght in the process of the spell? Had she panicked and teleported away? Did something force her to?
Whatever the reason, nothing could change the fact that Twilight was gone.
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Twilight collapsed on her bed, fear and exhaustion taking over her body. She weakly crawled under the covers, determined to sleep.
Her eyelids lowered, and Twilight fell into slumber.
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''She's...gone?'' Celestia's voice no longer held her calm demeanor - instead it was filled with fear, worry and sadness.
Luna nodded. ''We didn't kill her, don't worry. We could sense the traces of teleportation magic in the air.''
Celestia sighed. ''But Twilight would never have run from us without coaxing.''
''We did use the most powerful spell in the world on her, just after pulling her into a dark room and telling her nothing about it.''
The elder sister shook her head. ''No. She trusts me as much as she does her own parents. She would've felt fear, yes, but on her own Twilight would've stuck it out.''
Luna bit her lip. ''You say 'on her own'. Do you fear the same as us? That the nightmare lurks in her, already awakened and strong enough to talk to her?''
''Yes.'' Celestia couldn't say any more than that.
Luna stomped a hoof, tail flicking in agitation. ''We will not give up so easily. If it can talk to her now, it can influence her dreams.'' Luna shuddered at the dark dreams she had endured whilst being coaxed into the darkness.
''We will go to Twilight Sparkle, in her sleep. We shall combat the nightmare and tell her the truth!''
''Lulu, we're still weak. You ca-''
''Celly, if we wait any longer it will be too late. This is happening even faster than...'' Luna trailed off, not wanting to talk about her past so soon.
After a moment's silence between the two alicorns, the elder spoke.
''Go.''
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Twilight was stood on a platform, looking down on the same mass of darkness that had haunted her dreams only a day before. This time, though, a dark shadow was stood beside her.
''You are the Nightmare, I presume?'' Twilight's voice held no fear - only thinly veiled curiosity.
The shadow nodded.
''Good. Number one, why are you the reason my mentor tried to kill me?''
''Twilight, I am not the only reason. I only told you that so you would not try to fight back.''
Twilight blinked. ''Fight back?''
''Yes, Twilight. The truth is you are powerful. Me becoming a part of you amplified this power.''
Twilight took a step away from the figure. ''Woah, woah, woah. Stop right there. You're a part of me?!''
''Yes. On the day you tore me away from Luna, I bound myself to you.
On the day I tore... ''Nightmare Moon?!''
''Nightmare Moon ceased to be the moment I entered your mind. Now only I remain - the Nightmare.''
Twilight frowned in confusion, putting her fear aside for a moment. ''The Nightmare?''
The shadow nodded. ''And now I need a name. What do you think, Twilight?''
''I'm the one asking questions - and you still haven't answered the first one.''
The Nightmare chuckled lightly. ''Ah, yes. Of course. You see, Twilight, you are the most powerful mare in the world - you defeated Luna while she was stronger than normal. You could easily destroy Celestia.''
Twilight snorted. ''No.''
''I didn't say anything.''
''I knew what you were implying. I'm not destroying anypony.''
''Are you so sure?''
Twilight was caught off guard at this. ''Of course! Well, I'd destroy you in a heartbeat, but that's not the point here.''
The Nightmare shrugged. ''Whatever you say. I can't do anything without your consent.''
Twilight blinked again, this time in shock. ''You...can't?''
''No. I'm not as bad as you think - I only help ponies see the light, and when they do they're practically wailing for my help. Especially Luna.
Twilight lowered her head. ''Luna let you do what you did?''
''She did.''
''That..'' Twilight trailed off. She tried to think of something to say that proved the Nightmare was wrong, that she was lying...but she couldn't.
''Well then, you may as well settle down. Even if I can't do anything, we can still talk. I'm wiling to tell you about my past.''
The Nightmare shook her head. ''No, scratch that. I want to.''
Twilight opened her mouth to reply, but suddenly everything seemed to get lighter. Her vision was filled with a blinding light, slowly taking on the form of a small alicorn.
Luna.