Princess Celestia was not sure what to expect when her sister, Princess Luna, burst into the Afternoon Day Court with a look of excitement she hadn't worn in some time.

Looking for any excuse to get out of the court, Celestia had been more than happy to follow her sister to a hallway she had almost forgotten about. But one look at the sole door in every direction, her confusion was replaced with a sense of pride, and not a little of a surprise.

"I was not expecting this. Not so soon. Or for her," Celestia said, as she and Luna stared at what looked like any other door in Canterlot Castle. Except for the cutie mark emblazoned on it.

Luna nodded, calming down slightly. "Nor did I. Or for it to appear for her as well. I was expecting somepony else if I am, to be honest."

Celestia nodded. It was not a knock on the pony in question, or the other as well. But she too expected this for somepony else first, but she would be lying if she said she wasn't happy to have been proven wrong.

"You know we don't know how this thing works Luna. Who is to say what makes it appear when it does," Celestia said, giving her sister a knowing look. "Besides. I think she might be offended you think of her like that."

Luna looked away, a faint blush coloring her cheeks. Celestia giggled. "Don't worry. I won't tell her if you don't."

Luna huffed in annoyance as she looked back at her sister. "So now what is to be done?"

Celestia smiled as she walked away, forcing Luna to keep up. "Now? We tell them. All of them. They have as much right to know as much as we do."

"Even though they cannot enter as well?" Luna asked.

Celestia nodded. "Just so. They will need to know that when it reopens, she will not be or look the same as she did when she entered." She shook her head. "You remember what happened to us?"

Luna couldn't help but giggle at the memory, Celestia joining in a moment later. For all the ruckus and mayhem it had caused, the reactions to the changes had been worth it in the end. "How long do you think it will be?" She asked.

Celestia shrugged. "I cannot say for sure. It didn't make sense for us at the time, and it hasn't changed that much in the years since."

Luna tapped her chin. "Even though Starswirl and Mage Meadowbrook tried to make sense of it."

Celestia nodded, smiling at the fond memories. "Indeed. Maybe this time though, she can find a way to understand how this works. She has more experience with time travel than either of us have ever had."

***

Twilight Sparkle wasn't sure why she and all of her friends had been called to Canterlot on such short notice. There didn't seem to be any looming disaster. She hoped.

That Princess Celestia had explicitly told her not to bring anything at all with her only added to her worry. Was thing some kind of special princess training? New Magic? Both?

And then there was also the fact that both Cadance and her brother were coming as well. Not that Twilight didn't mind seeing them of course. But it seemed odd that they too would be there.

Heck, she was going up to the Crystal Empire with Starlight and Spike to see them the very next week! So why would it be necessary to see them earlier? Cadance was due to give birth any day now. Traveling was something she shouldn't be doing.

It was only when they had been met by a Royal Guard squad at Canterlot Station that Twilight knew for sure that something was up. They had never needed an escort before. It only got worse as they came to the castle. Instead of meeting them in the Throne Room, Celestia and Luna met them in a hallway that seemed dug into the back of the mountain.

Celestia's smile seemed to grow on seeing them, but they could all see that there was something more to it now. Even Starlight Glimmer, new to all of this, could see something had changed in Celestia's demeanor.

"It is good to see all of you again," she said before looking at Starlight. "And you as well Starlight. Twilight has told me great things about you. I can see what she means.

Starlight blushed at the praise, even if a part of her didn't feel she deserved it.

Celestia looked behind the group. "Now we only need to wait on your brother and Cadance."

"We're here!" Came Shinning's voice as he and Cadance rushed up to the group, Cadance coming much slower than normal, now heavily showing her pregnancy. This also meant she and Twilight skipped their Ladybug Dance, which Twilight would admit she missed more now than she had before the wedding.

Cadance smiled sheepishly. "Sorry, we didn't get here sooner. The train was slow and then, well, I can't go very fast now can I?"

Celestia smiled gently. "It is alright Cadance. We would have waited for you." She looked at Twilight, who stood straighter if possible. "This is not a time-sensitive thing."

Everyone shared a confused look. "So what's up?" Spike asked.

Celestia placed a hoof on Twilight's shoulder as her eyes began to water slightly. "It is time for you to take your final step on becoming an alicorn Twilight. And I could not be more proud of you."

Twilight blushed as she hid behind her wings. Praise from her mentor, even if they were technical equals now, was something that always set her heart aflutter. "Thank you, princess, but I don't know what that means?"

Luna smiled as she stepped back from the wall. "We will show you," she said, as all saw a door that she had been blocking. Nothing about it seemed special until they saw the cutie mark emblazoned on it. It was Twilights.

Shinning scratched his head as he looked at it. "I don't remember ever seeing this door." Which was strange, for as Captain of the Royal Guard, he knew all of the castle like the back of his hoof. It was his job, and even if he didn't have access to certain rooms, he knew where most of them were in the castle. This wasn't on any known map or plan of the castle. Not even the unused designs from the very founding of the city.

Celestia nodded gravely. "You wouldn't have. This room does not exist on any map of the castle for a very simple reason."

"Why is that?" Fluttershy asked.

Luna gestured at the door. "This room only appears when an alicorn is ready to take their final step on becoming their full and complete self. It appeared to Tia and me long ago."

Celestia nodded, as her smile dropped slightly. "It was not easy for either of us. But it helped us become who we are today. It was time well spent, even if I didn't think so at the time."

Luna nodded. "As do I."

Starlight caught the way the emphasized the word time, and it got her thinking. "So what is it exactly?"

Celestia shook her head as she looked at it. "We do not know if it has a proper name. But we have always called it the Hyperbolic Time Chamber. Inside is everything an alicorn needs to grow into their full self."

"Like what?" Rainbow asked, giving the door the stink eye.

Luna shook her head. "It changes depending on the alicorn in question. All we can say is that it tests those who enter to their absolute limits and then breaks those limits. It pushes the mare to their absolute peak, and then helps them rise higher than even that."

Twilight looked at the door with renewed worry. "And now its asking me to enter?" She and Cadance shared a concerned look. "Shouldn't Cadance go first? She has been an alicorn longer than I have."

Celestia shook her head, looking at her niece. "The chamber chooses those who enter when the time is right for them to do so. Yes, Cadance has been an alicorn longer, but I feel there is more to it than that."

Luna smiled. "And it might not want to endanger our niece or the child she carries if it is anything like our own."

"And what's that supposed to mean?" Applejack asked with a frown.

Luna shook her head. "We could not explain in a way that makes sense. Neither of us could. What we see and do in there is for us and us alone to know and remember."

Twilight gulped as she looked at her cutie mark on the door. Maybe it was just her imagination, but it seemed to be calling to her. "And how long am I supposed to stay in it?"

Celestia grimaced. "That is an impossible question to answer Twilight. To us, it will only have been one day before you return. But to you." She paused before sighing. "Time does not flow as we know it to inside the chamber. It could be a year, or maybe less, to you before you come out."

Now Twilight was really worried as she and Starlight shared a look. Their recent time travel nonsense had left a bitter taste in both of their mouths.

On top of that, her travels through the broken timelines had hammered home Twilight's own mortality. Or lack thereof. Being immortal and ageless as she was, the final one hurt the worst. Equestria would one day look like that, no matter what they did.

But no matter what, something seemed to be compelling her to enter the chamber, and Twilight found she couldn't resist. In fact, she didn't want to resist it. Something had awoken inside her, and now she wanted to complete it, no matter what

Before she knew what was happening, Twilight found herself standing in front of the door.

Celestia nodded. "It is calling to you Twilight. It is normal." Her expression turned grim. "You will not need to bring anything with you. The chamber provides everything you will need to survive for however long you will be inside."

Pinkie Pie hopped over, a mad grin on her face. "What are we waiting for? Let's go!"

Luna shook her head. "Nay Pinkie. Only Twilight Sparkle is able to enter the chamber. No other will ever be allowed inside once she steps across the threshold."

That got their attention. Twilight drowned out the shouts and arguments that that was a load of horseapples and that they were all going with Twilight, consequences are damned.

Feeling a hoof on her shoulder, Twilight looked up into the face of her mentor, that motherly smile she knew so well once more where it belonged. It helped to calm her nerves.

"Good luck Twilight. And remember. We will be here for you when you return. No matter what shape or form that might take," Celestia whispered.

Twilight smiled herself. She couldn't help herself. Steeling herself, she pushed the door open with a hoof and stepped across the threshold.

Seeing the open door, her friends and family made a mad dash for it to follow her, only to be stopped dead in their tracks by Celestia and Luna's magic.

Spike though ducked underneath it and made a mad run for the door. Twilight wasn't leaving him alone. Not this time! But before he could get across the door, he bounced painfully off an invisible wall that had sprung up in Twilight's wake, even as the door began to close behind her. Luna's magic caught him before he hit anything else.

They all glared at the princesses, but could only watch helplessly as the door closed with a resounding boom, but not before they all caught a glimpse of what was inside an all-encompassing white.

Even as that sunk in, they watched in shock as the door to the Hyperbolic Time Chamber vanished without a trace. Leaving no indication that it had ever been there in the first place.

Author's Note

Okay, I admit. This is taking somethings from Dragon Ball Z. But it's not a proper crossover, so don't expect anything else from the franchise besides the Time Chamber. Cover art was done by Darksly-z.