It was nighttime, Twilight could see, and they were back in Luna's bedchamber, in the Castle of the Two Sisters. The destroyed mirror had been repaired, or perhaps it hadn't even been broken yet, and the moon princess could be seen pacing back and forth in front of the window, occasionally tossing her head and shaking it violently.

Her voice was muffled for a moment, changing radically in pitch and tone as she spoke, and Twilight stepped behind the wardrobe to listen in.

"You know that I'm right, don't you?" Twilight remembered this as the voice that would one day belong to Nightmare Moon. "That she's out there with those sniveling foals, letting them worship the ground she walks on and kiss her hooves. She's out there taking all of the credit for the banishment of King Sombra, while it was truly you who weakened him to begin with."

Luna's real voice spoke up then, sounding weak and frightened as her wings fanned out and back, bending as if trying to cover her own ears. "Stop it... please, stop it..."

"Celestia will never recognize you as anything but a lesser power. She will never, never permit you the love and adoration you desire. The love and adoration that she has known all her life and denied you."

"You're wrong! I-I won't listen to you anymore!"

"Oh really? Now, now, Luna, dear, you don't need to be so angry at me, when it's really Celestia you're upset with. You're ever so jealous of her... as you should be! You always knew they loved her more, look how they celebrate her daylight. They hide away and shun the nighttime. They fear it. They fear you."

"They don't! They don't fear me!" Luna cried. She let herself sit down in front of her mirror again, staring at the floor beneath her hooves, her wings folding tightly against her sides as she shook. "They don't fear me..."

"Don't lie to yourself, stupid filly! They have never liked you, and they never shall! Don't you see, Luna?! They will never love you, so naturally, they fear you! Show them your true power, and then will you gain power over them! Give them cause to fear you!"

"I won't! I don't want them to fear me... I don't ever want them to fear me... that's how King Sombra ruled the Crystal Empire, and I don't want the ponies of Equestria to suffer the way that the crystal ponies suffered..."

"Need I remind you that it was because Celestia intervened that Sombra was able to banish the Crystal Empire? You might have killed him if it weren't for her trying to outshine you once again!" Luna's entire body seized, tensing and almost convulsing as the fully-realized voice of Nightmare Moon screamed forth. "IT'S HER FAULT THAT THE CRYSTAL EMPIRE HAS BEEN DESTROYED! IF SHE WAS SO WEAK THAT SHE COULDN'T RAISE A SWORD TO SEVER HIS HEAD FROM HIS BODY, SHE SHOULD HAVE LET YOU DO IT! YOU WILL ALWAYS BE NOTHING, COMPARED TO CELESTIA!"

"NO!" Luna's voice cracked back to its true pitch, her head and body shaking violently as she gasped for breath. "No. That isn't true."

"Oh, but it is! Think, Luna. Why should Celestia be forever be showered with love and praise, while you are left with nothing but sideways glances and after-thoughts? Oh, I know why. It's because you're weak."

"I'm not weak!"

"You are! You were born of the darkness of a wicked, wicked deed, and so you are cursed by the weakness of your cowardly bloodline. You blackened your soul further when you exacted your revenge on the stallion who committed that deed. You were born to live in shadow, and the light of your sister will always undo you. You've always been weak, that's why you created me."

"I didn't mean to create anyone, especially not someone so horrible!"

There was a single, awful beat of sinister silence before Nightmare Moon's terrible laugh tumbled from Luna's throat and the silhouette of the night princess stood up slowly, drawing herself up to her full height. Her eyes glowed a dangerous, toxic green, and it was not Luna who spoke again.

"Horrible, am I? Well, then. Perhaps instead of wasting my time convincing you to overthrow your tyrant of a sister, I'll just do it myself. After all, Equestria only needs one princess. Why shouldn't it be me?"