This is not going to work, you know.
The disembodied voice reverberating through Luna's skull snaps her from her reverie.
"Hmm?"
I said, this is not going to work. We should attack now, and catch her by surprise.
Luna closes one teal eye and turns her head slightly to look off to the side.
"Maybe it won't, but We have to try. This isn't the same as last time. I will not become a servant to my emotions again."
Suit yourself, little one. But you would do well to remember that there is a fine line between optimism and naivete.
Luna snorts. "How could I forget? This whole ordeal was a result of my being naive. However, being banished to the Moon for a millennium is a steep price if We fail, so I prefer to say that I'm being... Cautious."
Paranoid, perhaps?
The voice somehow manages to gesture at the vastly complex spell seal surrounding them.
Luna smirks and turns back to look at the ominous night sky. "Just a precaution, Nightmare. Neither of Us can predict what will happen, and neither of Us want your tendencies to doom our efforts to failure."
Very well. I shall trust in your judgement.
"Of course. I AM the brains, after all."
A regal chuckle.
And I am the brawn, indeed. How could I forget?
Luna and her companion's mental conversation settles into a brooding silence. Tentatively, Luna breaks it again.
"Nightmare?"
Luna feels her counterpart's attention focus to her.
"Do you..." The Lunar Diarch hesitates. "...hate me?"
When Nightmare doesn't respond immediately, Luna feels like she might have made a mistake.
...Should I?
"I... I don't know, I was just wondering."
No, I don't hate you. I am not sure whether is better to have been created by someone's anger and hatred... or to not have been created at all. At any rate, there is little point in dwelling on our mistakes at this point.
Luna sighs wearily. "Yes, you are correct. I just... I couldn't face another betrayal, not after all this," she says, waving a hoof at the door where her Sister was going to barge in and try to destroy them.
I will never abandon you.
Luna turned to smile at the mirror next to her. "Thank you."
A shuddering rumble tore through the building.
It seems Our sister is here. She's not even trying to be subtle about it.
"That probably means she has mobilised the Elements, as We predicted."
Good. I'll show them what happens when you get involved with the games of gods.
"They also happen to be one of the most powerful weapons in the Known World, so..."
Oh, I know first-hoof how powerful they are. That doesn't stop me from appreciating a good fight.
"If everything goes according to plan, We won't have to fight them at all. They may command the near-infinite power of Harmony, but they're only mortals. Celestia just chose to get them involved in this mess."
Another tremor signals the enemy's approach. Luna's hearing picks out the crunch of heavy footsteps outside.
Hear that? She even brought the guard here to escort us. How cute.
"I almost feel sorry for them. It can't be good for your pride if the ones you are duty-bound to protect happen to be the two most powerful ponies in the world. And that when those two ponies have a miscommunication error, it ends up... Well, like this."
They could clearly footsteps now, one set sounding clearly metallic, as if they were shod in gold. Luna amplifies her hearing, and can just about pick up the susurrus of a hushed discussion.
I suppose this is it. A fitting choice of location by the way.
Luna looks around at the old castle ruins located within the Everfree Forest, the location of Nightmare Moon's encounter with the Elements of Harmony the night she returned from a thousand year exile on the Moon. She had to admit, it was kind of ironic.
The door explodes.
The huge metal portal buckles under the heat and power of a blast of magic from the outside. Stoically, the Goddess of the Sun strides in, flanked on both sides by six very determined looking mares. Resting around five of their necks are gleaming gems in resplendent gold necklaces. On top of the sixth head, a golden tiara with a purple star-shaped jewel shines brilliantly.
Opposite them, standing in the centre of the chamber, is an ebony alicorn with draconic eyes of the most beautiful teal. Despite being hopelessly outmatched, Nightmare Moon retains a defiant, regal posture. Even Celestia is intimidated somewhat by the presence her nemesis emanates, exemplified by the bluish-silver armour she wears.
"Greetings, Dear Sister. And hello to you, Element Bearers." Nightmare chirps almost cheerfully. Surrounding the ebon mare are ethereal chains that simply begin in mid-air, as if they took root in another dimension and penetrate through space-time. They do not restrain Nightmare Moon at all; instead, they surround her within the seal.
Celestia took no notice. She glares at her enemy with obvious hatred. "Begone, monster. Release my sister from your twisted influence!"
Nightmare Moon gazes at her for a few moments, then sighs. "Have you learned nothing, Celestia? We have already tried to explain ourselves to you before have we not?"
Twilight Sparkle and the others, who knew nothing of the situation besides the fact that Nightmare Moon had returned, looked to their princess with pursed lips and raised brows. Celestia ignored them.
"Lies! That was just you playing a sick game with poor Luna's mind!" The Solar Diarch snarls.
"We have told you the truth! Why do you stubbornly refuse to see us for who we are?!"
"YOU are only a tyrant, and a murderer! A fool who took root in my sister's mind and forced her to try and create eternal night!"
The black alicorn closes her eyes. "No, sister." Her eyes open to reveal two ordinary pony eyes, gleaming with mercurial tears. "We are all to blame. Me, Nightmare... And you."
All seven of the new arrivals recoiled at the new voice that drifted across from the mouth of the creature they despised.
"Luna...?" Twilight gasps, overcome by worry and terror. Fluttershy clamps her hooves over her mouth to dampen the 'eek'. Rainbow Dash and Applejack look shocked, but maintain their rigid posture. Rarity and Pinkie Pie just look incredibly sad. Celestia, meanwhile, narrows her eyes, evidently connecting the dots.
Nightmare's form shrinks and lightens as Luna speaks. "You all believe Nightmare Moon to be some demented spirit that came to me at my weakest, and used my power to try and create eternal night. I'm afraid that is not true. Nightmare Moon is formed from countless centuries of repressed feelings of loneliness, anger and jealousy. Eventually, these emotions formed their own consciousness. And Nightmare and I... we became friends, I suppose. She saw my sadness, and sought to make it better. Unfortunately, she has a crippling lack of tact."
Luna smiled gently. "But we are almost one and the same, Nightmare and I. I can't lose her again."
Celestia looked at her grimly. Then shook her head, slowly. "No. I don't believe you. Nightmare Moon is just using you as her puppet."
Her horn glowed with heavenly light. "Prepare yourselves!" The element bearers quickly got into battle-ready positions.
The dark mare standing before them just stared, before laughing, a twisted fusion of deep and powerful, and light and mischievous. The chains suddenly snapped out, pulling the six smaller mares out of the fight and binding them tightly.
She laughed at Celestia's look of horror. "Discover check. You never were very good at chess, were you Celestia?"
And with a echoing roar, the Princess of the Night leapt at her sister.