Author's note: I really appreciate all of the kind words and encouragement. Thank you, and I think that this will get the plot rolling at an acceptable clip.
It was seven days until Twilight heard back from Luna. Seven long and lonely days of waiting and uncertainty. The letter she sent had been brief, a mere summary of her discussion with Celestia and a simple request at the end for a talk.
Twilight hadn't talked to any of her friends in Ponyville about Celestia; it seemed too personal, somehow, to involve them without knowing more. So, she read, and slept, and endured. She hadn't cried. She couldn't. She was still so angry, so uncertain about it all, that it felt like getting sad, properly, deeply sad at the thought of losing Celestia, would be too great of an acknowledgment that it was an actual possibility.
Spike had been cautiously optimistic. Perhaps, Twilight mused, because she hadn't been attempting to travel back in time or enchant the town. She would have, if she had thought it would save Celestia.
Twilight idly wondered what exactly she would be willing to do if Celestia's life were threatened by some external threat. She had faced Discord, she had faced Nightmare Moon, she had done many things, for Ponyville and Equestria.
But Equestria and Ponyville were abstract things, places. Celestia was a pony she loved, a pony she wanted to protect, honor and cherish.
What exactly would she be willing to do to keep her safe?
She was interrupted from her thoughts by Spike, who held a dark blue scroll fastened with an onyx bit of wax. After thanking him, Twilight went upstairs and closed her door, wanting privacy to read Luna's response.
She took a deep breath and broke the seal:
“If you would speak with me, come at the middle hour of the night to the old Royal Castle.
--Luna”
Twilight stared at the letter and read it again. She didn't know what she expected, but she thought Luna's response would be something more... substantial than this. She shook her head. Luna could be as cryptic as she wanted, so long as she would help.
Feeling a little less burdened than before, Twilight marched back downstairs to find Spike. After a brief investigation, she found that he had busied himself in the noble pursuit of taking a nap, so she left him as he was and wandered outside to find a way to kill time while she waited for night to fall.
Seeing that the market was still open, she walked over to find Applejack's stand. There were only a few ponies there this late in the day, and AJ had sold all but the last of her apples. Applejack looked at Twilight and smiled.
“Well aren't you a sight for sore eyes, Twi! I haven't seen you much at all this week.”
“I know, I've just been really busy with a project.” Twilight managed while sporting a weak grin.
Applejack narrowed her eyes.
“Spike said you've been moping around, that you haven't been working on much of anything.”
“Oh?”
“He also said that it seemed like you were hiding something. Not telling the whole truth, leastways.”
Twilight was the perfect image of indignant confusion.
“I don't know what you're-”
“You ought to know by now that lyin' to me isn't exactly the most productive of activities.”
Applejack softened, and continued, “But I understand if you need some time to think if something's bothering you.”
Twilight half nodded at this and picked up one of Applejack's remaining apples before she responded, “Applejack, I can't talk about this now. It's about Princess Celestia, and that's all I'll say for the moment.”
“You aren't going to start waving magic dolls around again, are ya?”
“I don't know, I still haven't gotten the last one back from your brother.”
A ghost of a smirk spread across Applejack's face before it faded and she replied, “Twi, I don't know what's going on here, but I can tell it's more serious than before. You should talk- if not with me, then with Rarity, or Fluttershy, or any of your other friends. You can't solve everything alone, you taught me that.”
“I haven't forgotten, and I think I might have found just the pony to talk to about this tonight. Thanks, AJ. I won't let this get out of hoof.”
Twilight turned to walk away, but Applejack's voice rang out as she left:
“You can have the apple, by the way!”
Twilight smiled. Amidst everything else, she had forgotten. Sometimes the little things made all the difference. She took a bite of the apple and walked to the park, wanting to watch the sunset. The sky was glowing shades of pink and purple as a late summer sun dipped below the horizon, and the trees and ground looked almost as if they were lit aflame, orange and alive amid the dying of the light.
Twilight settled down to eat, and produced a pair of sunglasses to watch. It was too beautiful to look away. All too quickly though, the apple had been reduced to a core, and the embers of the sun had faded to leave a somber darkness in its place. She felt cold, somehow, even though the summer air was still warm with the memory of day.
Standing, she stretched and looked back towards the town, then turned away and walked with purpose towards the gloom and isolation of Everfree Forest. If she wanted to keep her appointment with Luna and travel safely, she had to start walking now.
The walk was quieter than she had expected. The sounds of the forest grew to be part of the unconscious background after a while, and though the path was circuitous and filled with obstacles, she didn't encounter any manticores, dragons, cockatrices, or anything else unseemly. As she reached the bridge that separated the old Royal Castle from the Everfree Forest, Twilight wished she had brought Owlicious with her; his eyes were so much keener in the night than hers. Not wanting to trust that the bridge's flimsy supports would still hold, she teleported across the chasm and lay winded on the other side before picking herself up and walking to the castle steps.
With a sense of déjà vu, Twilight walked up the steps to the room where she and Nightmare Moon had once stood, where the heart of darkness had been at its most formidable. She shuddered, and pressed onward.
When she finally reached the top of the castle, the darkness hung as heavy as curtain in the air. The room was dank, and what little of the moon's glow could be soon was from small cracks in the castle's stone. In the very middle of the room, Twilight saw a tall figure shrouded in a colorless robe. With some trepidation, she walked closer, noticing that a dark blue light emanated off of the her.
“Luna?”
The figure turned and reached up to remove her cowl. It was Princess Luna, looking more solemn than Twilight had ever seen her.
“Twilight. Do you know why we're meeting here?”
Twilight considered, and then said simply, “No. Why didn't you just respond in the letter? Why all of these theatrics?”
“These are NOT theatrics. Twilight, I have been aware of Celestia's intentions ever since the wedding. I've been talking with her about what I consider to be a colossal mistake. But,” Luna paused in an awkward silence before she continued, “I cannot talk about her choices with you or anyone else.”
Twilight took all this in before she hesitantly asked, “Luna, are you afraid to disagree with Celestia?”
Luna shifted uncomfortably.
“I've been very careful since I coming back from my exile to avoid a repeat of past events. I, and others, would see a public disagreement with Celestia as the start of a path that leads only to treason. For that reason, I will speak of Celestia with you tonight, but no more. Twilight, no one must know of our talk.”
Luna looked directly at Twilight and said, “So to answer your question: No, I am not 'afraid' to disagree with Celestia, merely cautious in my doing so.”
Twilight sat down, suddenly unsteady on her feet. Luna was supposed to be the voice of reason, the cavalry, the indefatigable force that would convince Celestia.
Twilight looked up at Luna, unsettled that her plan had run aground so quickly, and said, “Have you had any success in talking to her? Any indication that she will change her mind and renew for at least another year?”
Luna walked closer, the darkness obscuring her face until a beam of moonlight happened across it, revealing worried resignation. She looked down at Twilight and quietly began, “I have not. I have been speaking against... the 'idea', but I haven't gained any ground. Celestia is convinced that the realm depends on her far more than is good, that her eventual passing will ease the realm into sufficiency, and that she will enjoy life all the more if it is finite. She is convinced that meaning only exists if her life will one day end.”
Luna closed her eyes and continued, “At least, that is what she tells me, the reasons she gives. I don't think that she truly believes that her life until now lacked meaning or purpose, but the Changelings' attack changed something in her estimation, that is apparent. And now she will forever be lost unless I can convince her by next Summer Solstice.”
Twilight felt her eyes beginning to well up, but she blinked away the tears, unwilling to accept the sadness because it would mean accepting Celestia's demise. She rose, unsteadily, and walked to Luna, carefully avoiding broken cobblestones and other debris that littered the floor.
Luna opened her eyes before Twilight said, “Luna. It is impossible that Celestia be lost to me in this way. It is unacceptable for her to continue down this path.”
It was well that Luna had picked such a secluded meeting place, as Twilight's voice grew louder and more frantic, echoing in the largely empty hall, “If she can't be convinced, then we have to find a way to protect her- from herself! We need time, and the summer solstice is just months. Would you be able to turn Celestia to stone, to send her to the moon, something, anything to delay? Would you-”
Luna put a hoof to Twilight's mouth, and warily looked around the empty hall before responding, “Twilight, this discussion grows close to open treason. It was once immediate banishment to speak thus, abandonment to the wild and the cold, for Equestria was a wilder and harsher place than you know, and the laws were harsher and stricter of necessity. Celestia has informed me that the land is no longer so wild, the laws no longer as strict.”
There was a heartbeat of silence before Luna began again with a smirk, “Although, since I have returned, I have borne witness to a Parasprite infestation across the realm, Discord's return, and the most widespread Changeling infiltration in recorded records for five hundred years, among many other minor calamities. How much calmer is Equestria, truly?”
Twilight stood, and looked Luna directly in the eyes. Her voice was hard as flint as she demanded, “Arrest me, then. Throw me in a dungeon, or banish me to the moon. But don't abandon Celestia to this and claim that it is treason to do otherwise.”
Luna's expression became pained, but she didn't back down. “If Celestia gets her way, and she almost always does, then I will be the sole monarch, and the nation is not yet ready to govern itself. If the realm is not to descend into chaos, then there must be continuity. I have to be trusted in order to fill that role.”
Twilight felt trapped. Luna could not, would not help her, and her reasoning was sound. Equestria needed a monarch, and Luna's duty to the realm prevented overt action against Celestia. Even if she succeeded in freezing Celestia in stone, the Castle Guard and the rest of the realm for that matter would never allow it. Anypony would assume that Luna had become Nightmare Moon again, or that they simply couldn't trust Luna as a Princess. After all, currently living ponies had known her for only the better part of a year, and faith was slow to build when ponies still primarily remembered you as a bedtime story to scare foals.
Luna smiled sadly, and looked at Twilight with fondness. She seemed to know what Twilight was thinking.
Twilight began to speak, but was cut off by Luna, “I will not arrest you, Twilight Sparkle. You bear neither me nor my sister any ill will, and you have always been my sister's faithful student. I would implore you, however: if you care about my sister, speak with her. Talk with her every day. If I cannot convince her that she is in the wrong, perhaps you can.”
“Of course I'll talk with Celestia,” Twilight said, “I've been avoiding her because I had hoped that this would go away, that she would change her mind. I'll keep fighting for her, though, however I can.”
Luna smiled.
“I would expect no less from the Element of Magic and my sister's personal student. Allow me to send you back to Ponyville. The forest is not safe at night.”
After a nod, Twilight was swallowed up in a starry blackness, and deposited right outside her house in Ponyville with not a flash or the slightest of sounds, merely a temporary parting of the darkness as she filled the formerly empty space.
Twilight looked up at the moon one last time before sighing and opening the door. She had less of an idea of what to do than before, but she was simply too tired to go on.