Four knocks in rapid succession left no doubt as to the pony on the other side.
"Come in, Luna," called Princess Celestia.
Princess Luna stepped inside and closed the bedchamber door behind her. Celestia was currently seated on her spacious canopy bed. Philomena offered a friendly squawk to Luna from her cage.
"Twilight is resting in the Palatial Suite," said Luna, after a brief nod to the bird.
"You put her to sleep, you mean," said Celestia, giving her sister a cross look. "I assume that's what took you this long."
"She asked me to!" said Luna, defensively. "More or less, anyway. The poor thing was mumbling powers of two under her breath; probably a compulsive habit due to anxiety. After several minutes of cajoling, I offered to help her to unwind, and she consented."
Celestia sighed and lay back onto the bed. "Lulu, do you think she hates me?" she asked.
Luna laughed. "You must be joking! Celie, nothing could be further from truth. That pony worships the earth you clop upon," she said. "Even moreso, now that she understands why you have been keeping her at a leg's length. Although..."
Celestia sat up. "What is it?" she asked.
Princess Luna sat on the edge of the bed next to her sister and brushed her mane to the side. "Since your release, your guard has been lowered in the company of friends. I regard this as a good thing. That said, it has brought something new to my attention," said Luna. "You feel things for the filly, do you not?"
A deep blush met Celestia's cheeks. "There aren't many ponies in whom I can confide, and she reminds me of a young navy-pelted pony I once knew," she said.
"That is most sweet. Compliment accepted," said Luna, with a smile. "But with regard to Twilight Sparkle: do you believe you felt this way about her prior to your last 'renewal'?"
"Based on the strength of what I wrote about her in my notes, I suspect I probably did," said Celestia. "It worries me. A crush on Twilight from before seems rather... repugnant."
"Repugnant? I fail to see why."
"Her age, of course, not to mention the fact she was my student," said Celestia.
"Ah," said Luna, with a mischievous smile. "Fear not: you are still robbing the cradle. Even if she is mostly an adult now, you remain hundreds of times older than she."
"Hmph. That isn't fair. For the moment, I can only remember dozens of times," said Celestia, and then her voice dropped in timbre. "Perhaps I'm better off this way."
Luna's eyes widened. "You are getting cold horseshoes about recovering your memories!" she accused. "Wherever for?"
Princess Celestia looked away from her sister. "The only thing I know for certain is that, right now, I'm happier than I can remember being since foalhood," she said. "And there is the matter of history repeating itself."
"Sister, I believe that is the problem we are attempting to resolve," said Luna.
"Not that history. I mean my relationship with my students."
"Go on," prompted Luna, a curious look on her face.
"My notes chronicle mistakes I've made at the beginning of each cycle," she said. "There is one mistake I keep repeating, despite dozens of warnings. Almost every time I take on a protégé, I lose them after the next renewal," said Celestia. "Just for the most recent example, my previous cycle began on 984 Anno Solequus. I've already told you about Sunset Shimmer, haven't I?"
"Yes," said Luna, her ears drooping. "Such a sad case."
"I took her under my wing in 972 Anno Solequus. In the Autumn of 984 A.S., mere months after the Lethe casting, Sunset requested a sabbatical. She seemed to need a break, so I granted it," said Celestia. "My notes were extensive, but insufficient for me to read her emotions correctly. I thought the filly was shy, because she was afraid to look ponies in the eye when speaking to them. Only too late did I learn that I was the only pony whose eyes she would not meet. She never returned from that sabbatical."
"Sister, you cannot be certain this was your fault," said Luna. "There are many reasons the young mare could have been a poor fit for your tutelage. Some of the burden must lie with the student."
Celestia sighed. "Perhaps, but the student before her left no room for doubt. When I accepted Starlight Glimmer as my protégé in 960 A.S., I hadn't attempted to take on a student in more than a century's time," she said. "That filly was extraordinary, which is why I took her in despite her being almost two years past the standard entrance age. In some ways she had more raw power than even Twilight."
"That is... disconcerting."
"Then, Lethe was cast in 968 Anno Solequus. This time, I managed to keep her as my student for a few years after the memory loss, but one day she left without any warning. She didn't even bother to say goodbye. Instead, she left this." Celestia reached out to the bedside table and lifted a note that had been lying there.
The note looked as though it had been scribbled in haste.
Dear Princess Celestia,
I realize now that our 'friendship' was just a one-sided lie. I'm a foal for trusting you for so long. For a while there, I actually thought we were close. I thought you viewed me as a peer rather than a subordinate.
You think you're better than everypony else because you're powerful. Well, I'm not any less important to Equestria just because I'm not an alicorn princess. I deserve to be treated with equal respect. Everypony deserves to be treated equally. That's what true friendship should be. Someday I will make you see that.
I hate you.
–Starlight Glimmer
Some of the writing was mottled by small drops of water. Some of the drops were fresh.
"Oh, dearest Sister..." Luna whispered, hoofing back the note.
"And do you know the worst irony of all? I didn't want to keep this note. I wanted to burn it," admitted Celestia. "But I had no choice. This is something I must remember, even if I don't want to. I can't get rid of this letter, because having it is the only way I'll remember. It's... evidence," she said. Her eyes shimmered, and she turned her head away from Luna as she placed the note back on the table.
"Celie, someday you shall set things right," said Luna, craning her neck slightly to get a better look at her sister's face. "The sooner we restore your memories, the sooner we can mend these fences."
"She's still out there," Celestia continued, with a sad smile. "Last I heard, she enslaved a small village and tried to kill Twilight. I doubt we've seen the last of her."
"I do not wish to be a broken recording cylinder, but we need to make you whole again, sister. Every story you tell illustrates precisely why this is so important," said Luna.
"But are you sure it's the right choice?" said Celestia. She turned back to Luna. Princess Celestia wasn't crying, but her eyes looked very tired, like a pony who hadn't slept in a week. "I'm starting to think ponies weren't meant to live for hundreds of years like this. What if the damage caused by mistakes and errors accumulates over time? No pony being has lived as long as I have, Lulu. Saddling myself with many lifetimes' worth of weight could drive me completely mad. It might be impossible."
Princess Luna paused for a moment, and stared nervously at the wall. Then she turned back to face her sister, with a look of firm resolution on her face. "No matter how large the ocean is, remembering things will not make you a different pony, dear sister," soothed Luna. "You are only the boat that rests upon the waters."
"I'm not certain that's true," said Celestia. "The experience of consciousness is tied inextricably to a coherent set of remembered events. Our memories are a large part of who we are as ponies."
"Yes, yes, I know," said Luna, waving a hoof in the air. "I have read Twilight's dissertation on the topic. But it matters not. Even if the memories have been locked away from your mind, the pony you have become because of those experiences is the pony that sits beside me now."
Princess Celestia sighed and swallowed an empty throat. "When I read my notes from cycles past, it feels like they were written by an entirely different pony. Or, different ponies, even," whispered Celestia. "It's hard to explain."
"I know you are afraid, Celie. That is normal," said Luna. "But think of Twilight Sparkle. Your feelings for her surely are influenced by your past experiences with her, whether or not you can remember them. Your love carries over."
"Well, perhaps. It makes for a tempting fiction to blame my feelings for Twilight on experiences I can't remember, but I'm not convinced. Once I go through with this, there won't be a convenient flaw within me anymore that I can blame my feelings on," said Celestia. "I'll need to take responsibility for my emotions, even if they seem overwhelming and foreign."
Luna leaned in against her sister and booped their muzzles together. "My darling sister, welcome to being a pony," she said with a smile, then leaned back and cupped a wing around her withers. "I can promise you that your friends will be here by your side to help you with those emotions. So, shall we proceed?"
Princess Celestia leaned into her sister and gave her a firm hug, then lay back onto the bed. "Let's get this over with," she said. "You know how to cast the spell, I presume?"
Luna nodded. "It is a classic. I have used it many times to recover dream memories, even over the past year."
"All right then. Here goes everything," said Celestia, and her horn began to glow.