Decades have passed since that fateful day, in a cave at the edge of the world. Since then, Twilight had traveled the world in the search for techniques and skills that might help her one day, preparing herself for when the vault she had sealed inside her mind opened once more. Every ounce of training was put to the test one early spring morning, and even after all her hard work and training, Twilight still had trouble handling all of the power that she had earlier suppressed. As luck would have it, the opening of the vault also returned the memories she had gained from beyond the world.
Combining her training with her returned knowledge, Twilight still struggled with her returning power. The only way any other pony might have known this, however, was if they had noticed that the sun had risen almost an hour earlier than usual. That particular feat was the only action she could take that would be able to manage her excess energy in a quick, but safe, manner.
Twilight Sparkle was whole again for the first time in years.
~~~~~~~~~~~~~~~
The invitations that each and everypony had received for Twilight's party were quite unexpected. The unicorn wasn't really known to be incredibly social, but here she was hosting her own party with more than just her family and friends. Many games were played and jokes were told, some might have said that it very nearly rivaled one of Pinkie Pie's own extravaganzas. Very few had suspected the true intent of the gathering. Twilight was saying goodbye, one last time.
The royal sisters had always held suspicion that this day would come eventually. They were also the first to know of Twilight's intention to finish what she had started, and, in accordance with Twilight's wishes, they told nopony else.
Twilight's oldest and closest friends were the only ones who remained once the party began to wind down, and the others returned to their homes.
"D'ya mind tellin us the reason y'all gathered us here today?" The old farmpony asked.
"Yeah, it isn't like I don't enjoy every party, but one thrown by you must be super special!" Pinkie Pie chimed in.
"It feels as though we haven't seen each other in ages, can't a pony just have some fun from time to time?" Twilight's answer wasn't very convincing.
"Darling, don't act as though we haven't known you for years. I think that we can tell that you're hiding something important."
Her friends, the first ponies she met upon her arrival to Ponyville all those years ago, were all looking at her now, each and every one of them wore a look of utmost concern about their faces.
"Y-you don't have to tell us if you don't want to." added Fluttershy in an attempt to alleviate Twilight's obvious tension.
After regaining her memories, Twilight had never realized just how much she owed to her friends. Even before her time in the void, she had grown distant in her search for answers regarding Starswirl's research. When she sealed her memories, they were there to help her fill in the gaps. Fluttershy, Pinkie Pie, Applejack, Rainbow Dash, and Rarity, each and every one of them would stand by her side until the very end if she let them, and she was grateful for that. To think she originally intended to simply disappear without telling anypony of her objective.
"Thanks Fluttershy, but I think it's about time I told you all everything..."
Her friends had held any questions they might have had until the end of her story. Their stunned silence at Twilight's admission of guilt in regards to her crimes made her feel more terrible than any actual punishment she might have received from her mentors. Afterwards, Rainbow Dash was the first to break the awful silence that had begun to hang in the air.
"So that's what this is all about? You didn't finish something you set out to do all those years ago, forgot about it, and now you're all set to go back and fix everything without telling anypony?"
"It's not that simple-"
"You're darn right it's not! 'Cause we're going with you!"
Twilight looked at each of her friends. She was still hesitant to have them there with her should the worst happen, but it was clear she wasn't going to change any of their minds about this. "Alright, you can come with me to the Null Tether, you all deserve that much at least." Twilight resigned.
"And just how do you propose to get them all there?" Asked Princess Celestia as she gracefully landed next the the group, Luna following quickly behind.
"Well, I haven't really had a chance to work out the details yet." Twilight admitted.
Luna stepped closer to those gathered. "Then you must allow us to assist you."
~~~~~~~~~~~~~~~
Instead of boarding a ship such as The Transcendence for the second trip, the entire group was led to a recently renovated room beneath Canterlot Castle. Secured by a designated guard detail, the room contained a single Translocation Glyph carved into the floor.
"Wait a minute between spell activations so that each group has time to get off of the glyph before the next cast." Celestia cautioned.
As much as Twilight was impressed on the level of foresight that the sisters had displayed, she was still taken aback by what she saw once she reached the other side. Not only had they added a matching set of Glyphs set to take them to the chambers just outside of the room housing the Null Tether, the sisters had also prepared some very specific materials. There was enough Flux prepared to activate the Remote View Spell several times over.
When the princesses came through with the last group, those who were visiting for the first time began to wander around in exploration, Luna following close behind to ensure that nopony got themselves lost. Twilight decided, instead, to ask Celestia about the preparations. "When did you feel the need to set all of this up?"
"Soon after we had learned about the extent of your memory loss." replied Celestia, "My sister and I figured that the circumstances surrounding your return were less than ideal. Even if that were not the case, and you had managed to protect our world from disaster on your first attempt, we thought it would be prudent to prepare for the worst."
"So, even after I sealed my own memories away, you suspected that I'd return here someday?"
"Our reasoning was influenced by our suspicion that you gave yourself a way to unlock those memories for a reason. Given the circumstances, we could think of no other reason that you would choose to do such a thing."
Twilight thought back to when she activated the recall while she was in the Void, "Since my memories have awoken, I've often wondered if I did the right thing, if my decision to come back was a selfish one? I came back here to live my life, all the while condemning countless worlds to their deaths."
"The situation surrounding your return is not something we can leverage against you. You have been quite successful in ensuring that nopony else know what exactly lies beyond the Tether, after all."
"There are rules. Rules that I am required to adhere to, that restricted my intervening with other worlds. If I'd stayed, I might have found a way around them eventually."
"And who is to say that it was even possible for you to save them. I do not think that that is the reason you chose to return."
"I suppose that's true. My solution to all of this, it's finished, and it has been ready for activation since before my return. Only, I'm not sure what will happen to me once it starts. I can only ensure that it works properly if initiate it from the other side. I believe that it has a high chance of severing any and all connections to this world. That includes my Remote View spell. There’s no way to know what’ll happen to me if the spell attached to me is interrupted... I guess I just wasn't looking forward to the possibility of dying."
"It is no selfish ambition to want to live. Living the life you have, I should think you have no regrets.” Celestia looked towards the group gathered around her sister before continuing, “If it's any consolation, everypony appreciates the effort that you have applied thus far, even if they do not realize it themselves. Certainly nopony present harbors any doubt that you'll do the right thing."
She looked back towards her friends who had gathered near the arrangement of Glyphs. Twilight knew that they could only be supportive, but deep down she wasn't sure she could deal with putting her friends through whatever happened next. "Princess Celestia, I want you to promise me something."
Celestia only looked upon the unicorn in silence.
"If-If I don't come back, could you make sure that my friends are taken care of."
"I promise, Twilight, but I think that it would be best not to dwell on the worst possible outcome."
~~~~~~~~~~~~~~~
Once Twilight recovered from her trip through the Tether, she turned to look upon her world one last time. A blue and green jewel that lay in stark contrast to the mottled darkness that was the Void. As she drifted some distance from the Tether's stream, Twilight called upon her console to initiate the shell's startup sequence. When it appeared in front of her as ordered, she found herself relieved that she didn't have to make her way up to the Focus to finish her task.
Pulling up the procedure she had left for herself, Twilight did a quick once-over to make sure everything remained how she left it. Nothing seemed out of order. "Console," she started, hesitating as she orientated herself for the best possible view, "Initiate the Shell Startup Procedure."
{Command Confirmed.}
{Initializing...}
Slowly, the spaces in between the octagonal-shaped lattice began to solidify into permanent barriers. The new shell was designed to be impervious, and Twilight watched as the multitude of lights that formed the Null tether became fewer and fewer, until only a trickle of light remained. 'The process would be over soon,' She thought as the last threads of light escaped the barrier. For the first time in Twilight's life, she was completely calm. No projects due, no experiments to run. Just here and now.
Twilight closed her eyes awaiting what she knew would be next. She did what anypony would do when greeting the end, she thought about all of the memories she had gathered throughout her life. Friends, family, life's ups and downs. All of it. Deep down, she felt the connection that held her to her body get thinner and thinner as the seconds ticked by, until finally the strain proved to be too much and the filament that connected her to herself finally snapped.
~~~~~~~~~~~~~~~
Far below in the cavern that housed the Tether, Twilight's friends watched over her with a variety of feelings. The two alicorn noticed the changes first. The lights that formed the Null Tether, which only they could see, began to fade. The once magnificent column of light was soon reduced to that of a simple stone structure.
Fluttershy was the first of her friends to noticed the change. "Are you okay Twilight?" She asked.
The unicorn's spell began to falter, the bright glow of the activated Flux beneath her started to dim as its magical bonds severed. Twilight collapsed.
Rushing to her aid, the group attempted in vain to revive their friend. Even going so far as to suggest bringing her back to civilization in hopes that she might be revived there.
Celestia and Luna only looked on the heart-wrenching scene, one they were far too familiar with. "My little ponies, I am terribly, terribly sorry. I'd hoped it would never come to this, but I'm afraid that Twilight is not coming back."
As each in pony, in turn, grasped the realization of their loss, their cries of mourning echoed off of the walls of the chamber.
“She always knew that something like this could happen.” Celestia added.
“Then w-why didn't T-Twilight tell usss...” Cried Pinkie while she fought back her tears.
“I believe that she feared that somepony might try and stop her. You all should be honored that she chose you as witnesses of her sacrifice. She did this so that we all might live on.”
The grieving continued for some time, but eventually Princess Luna offered to carry Twilight's lifeless form from the cavern, saying that it was the least she could do for somepony as special and heroic as Twilight Sparkle. Doing everything she could, so that she might save the ones she loved was something that all should aspire to, even if, in the end, it called for the ultimate sacrifice. The others gathered there tearfully shared their agreement.
Twilight Sparkle would never be forgotten.
~~~~~~~~~~~~~~~
{Process Complete.}
{Standing by for further instruction...}
"Wait, what!?" Twilight quickly wiped her bleary, tear-filled eyes so that she could read the console's output for herself.
{Process Complete.}
Yet here she was, alive and well.