2) Prologue in the Royal Chambers – present day

It was a beautiful night in Equestria, the full moon casting his quiet light through the clear sky, overshadowing the sparkling stars that were fighting an unwinnable battle for prominence of the horizon. All over the land ponies were asleep, working or enjoying the night while gentle silence settled itself over the kingdom. Even Canterlot had grown dark by now and only through a few windows was the soft light of a candle still visible. One of those candlelit windows was in the city’s castle, in one of the highest towers, the Tower of the Princesses itself.

Sitting on top of her overly large-sized bed, Princess Luna squinted at her tired sister warily.

“So, pray tell, sister, why art thou still awake at this hour of the day? Should thou not be in thy chambers and rest until the morrow?”

“I could ask you the same, dear sister” Celestia answered, smiling.

Knowing Celestia throughout her entire life, Luna could only think of one reason why her sister had come across her room to see that she was still awake.

“Thou were in the kitchens in search of one of thy cakes,” the Lunar monarch half asked, half stated accusingly.

Nodding and smiling guiltily, Celestia fully stepped into the room and closed the door behind her. “Well, you know… me and my sweet tooth these days.”

Trying to suppress a grin, Luna made room for her sister on the bed and waited patiently for the larger alicorn to settle down next to her.

“It doth not explain why thou are visiting us at this hour.”

“Do I really need a reason to visit my little sister?” The white Alicorn asked in mock offense.

Luna gave her sister a sidelong glance and shook her head, smiling.

“Well, now that I am here, is there something that keeps you up at night, Luna?”

Sighing in resignation, the Night Princess looked out of the window at her moon hanging in the sky.

“We were just wondering, since we came back to Equestria, we have seen ponies acting much more autonomous than was customary in our days. This, of course, is something good we presume. But we couldn't help but wonder… if we are still needed these days?”

Frowning slightly, Celestia looked at Luna. “What do you mean, if we are still needed?”

“Well… we have seen that our little ponies have had to deal with many problems since our banishment. What we also have seen is, that thou have decided to give them more and more power to handle them themselves. So, we were just wondering if we’re still needed in our kingdom… or if our little ponies would one day be able to handle themselves without thine or mine guidance.”

Realizing her sisters’ approach, Celestia smiled. “Well dear sister, as much as I would like to say we could give up the mantles of leadership one day, the truth is, that I’ve tried. I tried so very hard after you were gone. I thought that I could finally wallow in my own self-pity if I would just get them to be independent enough to no longer need us. But they came back every time. Each time I tried to push them away, more and more came back, asking for guidance, tutelage or help in some manner. Some might argue that they saved me from my own destruction, which I am eternally grateful for in hindsight, because I think, that if they wouldn’t have done so, I might have lost myself too and would never have been able to see you again, sister.”

Inhaling deeply and sighing, Celestia continued, “but you see, these days, they are so ‘autonomous’ as you had called it because it is a simple necessity to run such an extensive country as ours. Equestria has grown over the centuries. It has been difficult, Luna and even though I have had Cadence helping for the good part of five hundred years, Equestria is simply too demanding to be handled by so few. After all, we are the biggest country in the known world, dear sister. Our duties though… have changed over the centuries, too. While it saddens me, we can no longer hear out every one of our little ponies. We have to set ponies in charge instead of us to rule and govern what we cannot. But all in all, yes, we are still needed, now more than ever. Our ponies do not solely look up to us for guidance now. They see us as their head of state now. They see in us the values of our kingdom, the very values ponykind stands for. We are their immortal anchor through time now, dear sister.”

“But why, dear sister, did thou plan for thine niece to rule in the Crystal Empire rather than in Equestria?”

“Whatever do you mean, Luna?”

“Didn’t thou send Cadance away because of us?”

“I didn’t send her away because of you, Luna, what are you talking about?”

“After our return, thou sent Cadence away rather than letting her rule alongside us. Didst thou only use her as long as thou needed her until we were due to return?”

Celestia sat there, baffled.

It was a rare thing these days that something could give Celestia pause, and so it had only occurred once or twice this century, but right at this moment, Celestia lacked any words and simply stared at her sister in disbelieve.

“I love Cadance as much as I would love my own daughter. And I would never send my daughter away!" Celestia defended.

Suddenly she paused and flinched visibly as she realized that she had just run into one of Luna's traps. Finally understanding that Luna was trying to mislead her, she played along for now, "well, I sort of did, didn't I...? But only for the time being, the Crystal Empire needs her right now. I think more than Equestria does. After King Sombra, the ponies of the Crystal Empire needed to come to terms with the fact of their banishment just as much as you did, and Cadance is there simply to help them grow steady again. I never intended to send her away and as far as the plan goes, she will either leave the Crystal Empire one day to rejoin us in Equestria or the Crystal Empire unites with us.”

Now, it was time for her to finally take back control over the conversation, “as far as we can tell, the latter will happen in one or two decades. But… you should know all this already, dear sister. What is really bothering you, hmm?”

Looking back at her moon outside, Luna shook her head once and sighed.

“We can’t tell thee. We have to… um, I mean, I have to figure this out alone.”

To comfort her sister, Celestia nuzzled the smaller alicorn and switched to a much gentler tone. “You can tell me everything, Lulu. We may have been separated for one thousand years, but I had hoped to not have grown as far away from you as you might think right now.”

Relaxing at Celestia's nuzzles, Luna looked back from her moon to her sister and sighed again.

“The problem is thy former student,” Luna stated as a matter of fact.

“Twilight? Is there something wrong with her, dear sister?” Celestia asked, suddenly concerned for her former student.

Shaking her head and recoiling from her sudden slip, Luna tried to change her approach. “No, no… it's just… we thought we were her friend, one day, but… well, there is… we mean… well, after her ascension we…”

“Luna? Luna calm down, please.” Celestia softly rubbed her sister’s wing. “Just calm down, Luna and tell me what is wrong.”

With the telltale signs of beginning to cry, Luna nuzzled her head into Celestia's chest, as she did so many millennia ago when the two of them were still foals. After a moment of contemplation, Luna gave in and decided to tell her sister. After all, she knew Twilight longer than she herself did and practically helped to raise her, so, Luna figured, if someone could help her with her dilemma, it would have to be her sister. “After our return, we vowed to ourselves that we would protect those who were so kind enough to free us from our foolishness that much more. We vowed that we would guard their dreams to ensure that the six of them would have a pleasant life, and thusly that duty has been fulfilled, with just one exception...”

Luna choked down a sob. “But we can’t. We can’t help her... since this day, exactly five years ago, she won’t let us. She has to hate us. She has to… fear us.”

Looking down at her sister, Celestia was stunned again. Not only could she not imagine Twilight hating her sister, nor did she expect her sister to cry so suddenly. Stroking her mane carefully, she tried to soothe her sister as much as possible until she was able to talk again.

“Even after Twilight ascended, our vow did not change. Our protection would not waver. Our vigil would be a happy one for the fact that we would see her joyful and know we were a part of it. To our great dismay though, we fear our shame could stand now for the rest of eternity. We would rather help her and try to make up for our crimes, than see her writhe in her sleep every night. We should be forever in her debt, but she has shut us out,” Luna said, her voice cracking again.

“We want to be there for her as much as she was there for us, as much as she helped us and as much as she is still helping us… but she has shut us out. We don’t know how, nor do we know why, but… she… shut… us…” the Lunar Princess pressed herself against her sister, crying.

"Shhh, shhh, little sister," Celestia hushed, distressed by her sister's grief. The ache in her chest grew with each moment of Luna's labored breathing. That very same ache was telling her to do something, though she had no idea what. With the intent of knowing exactly what was causing Luna to cry so, Celestia asked, "From where Luna? Where have you been shut out?"

“From her dreams!” Luna almost shouted, shoulders sagging, as if admitting it out loud would be like admitting to being a complete failure. “We can’t access them, every time she has a nightmare, we have to stand there and watch without being able to help. We… we can’t help her. We can’t assist her. We just can’t look into her dreams and see what ails her, we just can’t, sister, we can’t.” The weeping alicorn sagged against her sister once more.

Celestia was puzzled. Her sister, the sole master, and discoverer of dreams was powerless in her own realm? In this very realm of dreams which indirectly sprung from her creating hoofs? She had never heard of anything even closely resembling the capabilities of accessing the dream realm and thought of it as impossible aside from her sister. She did not know what to say, so she continued comforted her sister further and waited for her to resume speaking.

“Five years ago, we and thy student sat in her library after one of her lessons for us to adjust to modern life. After her teachings, the two of us found ourselves in front of her fireplace and she asked us what our true powers were. She asked us how powerful Nightmare Moon really could have been and what she could have done to her and her friends,” Luna began to explain.

“We considered her and doubted she would have anything negative in mind besides her natural curiosity, but we didst not tell her this to spare her the dark thoughts. But we did tell her of our powers. We told her that we shepherd dreams. After hearing that, she changed. She began to act weird, but we did not question it. We simply thought it was one of her phases and ignored it. “

Tearing up again, Luna tried to press through, “b-but after we left that night and resumed our duty in the dreamscape, we found out that she had shut us out somehow. She had created some sort of force-field around her dream to shield it from mine presence and powers. This shield has remained unwavering for exactly 5 years. For 5 years now, we have been unable to enter her dreams. We are unable to mend her when she has nightmares, ... l-like today, and we are unable to confront her of this topic. Every time we bring it up, she shies away saying nothing. We are useless if we cannot even fulfill our base purpose. How can we call ourselves a princess, when we cannot even help those who we hold dear?”

“Shush, calm down, sister.” Celestia rocked Luna gently. “What would you think if I would help you and we simply ask her together once we see her the next time, hmmm? I am sure there is a logical explanation for all this and I am also sure that she does not hate you. After all, she does enjoy your weekly visits to her castle, I am sure of it.”

Sniffling softly, Luna glanced up at Celestia. “She does? How does thou know?”

“Well, for one, she said so in her letters. And two, she seems always so happy when you are around, so I doubt that she could ever hate you.”

“Art thou sure?” Luna asked, finally composing herself and wiping away some tears.

“I am certain, dear sister. Now, how about the two of us are going down into the kitchens and I show you the wonders of modern hot-coca.”

Snorting once, Luna glanced at Celestia, smiling. “Thou use every chance thou get to feast thyself on something sweet, doesn’t thou?”

“Well, what should I say? I am a simple mare, and when I have the chance to cheer up my sister in the process, I do it all the more gladly.”

And so, the two Alicorns left the room and went to the Royal Kitchens, where they found aside from the promised hot-coca a very selfish white noble stallion who was swiftly driven away from the kitchens by using cake leftovers and every throw-able item in range of the two alicorns. The impromptu food fight that was created in the process left the royal kitchens like a giant battlefield after the two laughing alicorns left the room, to the shock of the shortly arriving morning brigade of cooks and maids. After some time, the castle was finally silent again, as now, the two rulers reached their respective beds and fell asleep shortly after midnight.

Sorry for having to throw out some last minute corrections XD ... I was too eager to post it... one full day ahead of my plan.