Twilight was surprised when the flight took less than two hours, of course she knew that this was directly linked to Celestia's magic, 'the Princess wasn't kidding when she said I was needed immediately' Twilight thought to herself as the chariot began turning to face the length of the castle courtyard.
The second the carriage came to a halt, Twilight jumped out to stretch her legs. She left the bag behind; somepony would bring it to her room later. She looked around the gardens, nostalgia building up as she remembered her days as a filly, when she would sit in the courtyard for hours, just reading. Her memories were interrupted, however, by a bright, golden glow suddenly winking at her from one end of the courtyard, that heralded the arrival of the Sun Princess.
She walked gracefully towards Twilight, mane billowing out behind her, despite there being no noticeable breeze. All of the guard ponies bowed to the Princess, but Twilight ran straight up like an excited filly and leapt forward, clamping her forelegs around Celestia's neck like there was no tomorrow, with a wide grin plastered across her face. The Princess, obviously taken aback by this, stared on for a moment, but quickly pulled her protégée further into a heartfelt embrace, all the while smiling herself. Twilight could tell, however, that she was worried about something.
Standing there, it dawned on Twilight what she had just done, and she blushed profusely as she pulled away. It took a moment for the Princess to compose herself after this, rather intimate, moment with her mentee before she started talking, "My faithful student, how nice to see you again," Princess Celestia smiled, "if only it were under better circumstances," she added wryly, smile fading slightly. Twilight’s grin also lessened somewhat as they both acknowledged the seriousness of the situation.
"So, what is the emergency, Princess?" Twilight asked her mentor, who sighed deeply and turned around, so she was facing the way she had entered.
"Follow me, I will explain on the way," Celestia said, and started walking down the corridor, through a great set of double doors, Twilight quickly in tow.
"Before I explain what is going on, you probably would like to know why I didn't tell you the problem in the letter I sent," she added once Twilight had caught up. Twilight gave a nod in affirmation and Celestia continued, "You see, as your teacher, I am familiar with your habits and I knew that if I had told you what was going on, you would have likely overworked yourself trying to prepare for it, and I need you in peak condition for the task ahead."
Twilight nodded guiltily, knowing the Princess' words to be true. "So, what do I have to do?" Twilight asked.
"First, you must understand the problem, and I think the best way is simply to show you," Celestia replied, stopping in front of another pair of doors; Twilight had seen this door before, she’d explored much of the castle when she lived here, but it was a bedroom that no one ever used the last time she had checked. The two guards, who were standing at attention in front of the doors, stepped aside and bowed, whilst simultaneously opening the way to the grand bedroom they were guarding.
"What’s in here?" Twilight asked.
"This is my sister, Luna’s, room," Celestia replied, waiting for Twilight to walk in first. Twilight wondered why she had never seen Luna in her there before, but she then realised the reason and blushed. Luna was still on the moon when Twilight had lived here, and yet her room was still kept in top condition. The bed was always made; not a speck of dust was to be seen anywhere; and fresh flowers lay on the bedside. That sentiment hit Twilight as amazingly sweet, and she had to quickly walk into the room in front of Celestia to hide her now deeply crimson cheeks.
The sight that awaited her inside the room though, knocked all sentimentality from her mind, and replaced it with confusion, awe, and not a little fear. For hovering over Princess Luna’s bed was a sphere, constructed entirely out of magic. The deep blue colour made it instantly recognizable as Luna's own. It was so thick, however, that seeing clearly what was inside was next to impossible. Though barely visible, there was a silhouette of a pony thrashing around within it.
"Two days ago, Luna didn't show up to raise the moon, at first I believed that she was just late, and decided to sleep. An hour later though, the moon had still not risen, So my Personal Guard and I searched her out, fearing the worst; we found this,” Celestia pointed to the bubble, “My sister and I have a link as the two celestial alicorns, and also as sisters so I could tell that Luna was distressed inside there.
Normally, I would have been able to sense this from anywhere, but the bubble must have been muffling our link somehow, and I only felt it once I got close. Naturally, I attempted to break the bubble multiple times but to no avail. This is why I had to call upon you; I knew that you would be able to think of something," She whispered. Twilight nodded and turned away from Celestia to face the bubble. She stared at it for a good minute, deep in concentration while Celestia held her breath, hoping her student could think of a solution.
"Okay, I’m going to run a few tests, and it might take a while; I’m sure you have duties to attend to, I’ll be fine here," Twilight replied, already trawling through various possible solutions in her mind. Celestia nodded in reply.
"I will leave you to it then, good luck, my faithful student," The Princess of the sun said as she turned and walked out the door, closing it behind her and instructing the guards outside not to interfere.
Twilight sat down and looked up at the magical sphere, as her horn began to glow with a purple aura, tendrils crawled from the tip and probed the surface of the bubble; she could feel the magic and its owner. It appeared to be in some sort of self-defence state, whilst Luna seemed to be extremely distressed. She probed further, searching for a way to break the spell and free Luna from her own magic.
As the tendrils enveloped the bubble she could hear a faint voice in the back of her head, "Twilight Sparkle!" It seemed far away, yet very close, "It is I, Luna!"
Distress was obvious in her voice.
"Luna?" Twilight thought.
"Please, help me!" The voice replied, thick with worry.
"I’m working on it!" Twilight responded, pushing the tendrils further into the barrier and sinking them deeper into the surface, desperately trying to think of a solution. Hours later, or maybe it was just a few moments, they hit something solid, and Twilight understood.