Twilight Sparkle studied the ancient book which documented the work of Starswirl the bearded. Twilight was desperate to understand the Rainbow Power given to her and her friends by the tree of harmony, but with no tangible object to study, she would have to enter the metareal realm. Twilight closed the book, she now had a grasp on the spell and was confident she could cast it. She concentrated hard as her horn grew brighter and brighter. The magical energy then engulfed her and that was the first half of the spell complete. She was now encased in magic, but to do what she needed she needed to become one with the magic. Twilight’s horn sparked as she enacted the second half of the spell. Suddenly Twilight felt like she did when she became an alicorn. She opened her eyes and found she was no longer in the castle. She was in a world of swirling purple energy. Twilight nearly exploded with excitement, she had done it she was inside her own magic, something very few ponies in all of existence had ever seen.
Twilight concentrated on what she wanted and she felt her horn start to pull her. She soon found herself before six glowing shapes all connected by flowing rainbow streams. Twilight recognized the shapes as the cutie marks of herself and her friends. Twilight touched the butterfly mark and felt the presence of Fluttershy, which made her realize that the symbols must be a part of her friends that exist within her. Like the Elements of Harmony the Rainbow Power functions in conjunction with the group that wields them, each piece is an equally important part of the whole. But the Rainbow power is internal, rather than external, which meant Twilight had a submagical connection to her friends.
Twilight knew that as an alicorn her life span was now far longer than it once was, so she wondered when her friends would inevitably pass would this part of them remain within her? A part of them she could keep forever? Suddenly she had a thought. What if instead of keeping some them within her, she instead put some of herself within them? Almost as soon as she thought of it a glowing white orb, which pulsated with flowing energy appeared before her. Twilight knew that it was her own life force thanks to Starswirl’s notes, but the orb in his descriptions was much smaller. Of course Twilights was bigger, now that she was an alicorn.
Twilight looked at the rainbow strands that connected the cutie marks and knew all she needed to do was cast a simple binding spell to the orb to one of the strands, then all her friends would live as long as her. Twilight was about to cast the spell when she realized what she was doing. She was about to make her friends immortal without their permission, without even consulting them. Twilight imagined how angry they would be, but no one asked her she thought. Being an alicorn was thrust upon her for no other reason than it was her destiny, and without the six them Equestria would be without it’s protectors. Twilight shook her head, why was she rationalizing this? Was she really trying to convince herself it was the right thing to do?
Twilight imagined herself and her friends at the Grand Galloping Gala in 100 years. In that time the six of them had gone from being fish out of water, to running the gala. With dancing and real fun with Pinkie Pie, the high society types looking to Rarity for approval, maybe even a petting zoo for the kids run by Fluttershy. The Wonderbolts at that point would look up to Dash, and Applejack would be catering the whole event.
There was merit to the idea. She would ask them to consider it.
As Twilight began to mentally prepare how she would ask, and maybe convince, her friends an image popped into her head. Herself in a graveyard surrounded by tombstones each bearing a name and cutie mark of each of her friends. At this thought Twilight shut her eyes and felt magic in her horn. When the feeling went away Twilight didn’t open her eyes. She realized what she had done and wasn't ready to face it. Did she really do it? How could she be so selfish? Would it really have worked? She casted it out of reflex, it probably failed because she wasn't really concentrating.
Twilight opened her eyes hoping she would see things unchanged, but she saw a shimmering purple strand tethering the orb to the rainbows. It was done thought Twilight numbly. She had cast the spell and there was no going back.
Twilight knew she needed to tell her friends, but every time she wanted to bring it up she found she couldn't. Several times she called her friends together to only to chicken out and end up asking for advice to some made up problem or announcing some fun activity she pretended to have planned. At some point Twilight found herself making a list of the fabrications in advance.
Several years past with the secret looming over her. Twilight stayed silent when the Crusaders got their cutie marks, she stayed silent at Rarity’s wedding, she stayed silent when Granny Smith passed, she stayed silent when the crusaders graduated high school. Twilight suspected Discord knew, more than once he seemed to steer conversation to the subject, but Twilight never took the bait.
One day Twilight greeted Bon Bon in the street and noticed grey in her mane, and knew her time was up. Later that day Twilight called everypony to meet her at the castle. Before anypony could arrive Discord appeared and confirmed what Twilight had suspected, he knew. He offered to take responsibility, after all it wouldn't be that hard to imagine him doing something like this. But Twilight knew she couldn't pass the buck like that, after all, she was in this mess because she made a selfish decision, and another wasn't going to help. Even if nopony blamed her could she really cope with the guilt of having lied to everypony? No, she needed to come clean.
“Discord, I can’t keep hiding from what I’ve done. The time has come for me to admit it to everypony, but, will you help me?” Discord nodded and changed himself into a painting hung above the doorway. Soon Twilight was joined by the others. They stood there waiting for her to speak, but Twilight stood in silence. She looked up and saw Discord beckoning her on. Twilight tried to start, but only studdard, then she started trembling. Fluttershy recognizing something was wrong rushed forward to console her.
“Twilight, what’s wrong?”
“Well, you see…” Twilight started. She looked up again and saw Discord had turned himself into a picture of Starswirl the bearded, who noded to Twilight to continue. Even tho she knew it was really Discord Twilight was encouraged by the sight of her idol. “You see, a long time ago I did something. Something very selfish.” Tears started to well in Twilight's eyes.
Rarity stepped forward and said, “it’s ok, we’ve all made mistakes. I know too well the regret of putting myself first.”
“Yeah sugarcube,” said Applejack “just come clean, and we won't hold it against you.”
“You don’t understand,” said Twilight “what I did affects you, and not in a small way.”
“How bad could it be?” asked Rainbow Dash.
“It changes everything.” Twilight paused one last time before continuing. “As you know I am an alicorn now, and because of that my lifespan is far beyond that of a normal pony. I came to a point where I had to face that, and I imagined my life without all of you. In that moment I became so afraid I acted impulsively and cast a spell that would end that possibility.”
There was silence in the room. Then Rarity asked “what exactly are you telling us?”
Twilight didn’t look anypony in the eye when she said, “you will all now live as long as me. My ‘immortality’ has been extended to all of you. The Rainbow Power in all of us creates a bond that made it possible.” Anticipating the next possible question Twilight said, “it can be done with all of you and only you. I can’t bring anyone else with us.”
Nopony spoke, each one thinking trying to remember any clue they might have had to confirm Twilight’s claim. None could recall any signs of ageing, granted they still weren't old enough were it would be majorly noticeable, but the little things that should have happened by now, the small changes ponies of a certain age go through.
Rarity left the room saying nothing. Twilight believing their friendship over began to cry. Fluttershy hugged her and Pinkie Pie rushed forward to do the same.
“It'll be ok Twilight,” said Fluttershy, altho she wasn't entirely certain that was true. Rarity was the only one of them that was married, which meant she was the one who had the most to lose.
Rainbow Dash stepped up to Twilight. Pinkie and Fluttershy backed off as they could tell she had something to say. Dash unexpectedly wrapped her forelegs around twilight in a bone crushing hug. “Thank you Twilight” she said. “Thank you so much.” Dash dropped her and did some loops in the air before flying out the window and shooting into the sky.
Rainbow Dash had never felt so elated or so free. How could Twilight ever think she would be upset by this? Mortality was a burden she never knew weighed on her, but now that it was gone she felt a freedom she never knew possible. With infinite possibilities, Dash soard on to a boundless future.
Back at the castle the others were momentarily stunned at Rainbow’s enthusiasm. “There, you see” said Pinkie, “It’s going to be ok.” Pinkie honestly didn’t know what to do. She wanted to throw a party but wasn't sure it was the right thing to do. She felt the prospect of not dying was cause for celebration, but she also knew it meant saying goodbye to every single loved one. Every pony has to go to a certain number of funerals in their lifetime, but Pinkie knew she would now have to go to everypony's funeral. And no one, Pinkie realized, would ever go to her’s. Pinkie was also raised in a religious family, privately she had always looked forward to seeing loved ones again in Heaven. That was no longer a possibility for her. Altho she kept smiling a single tear rolled down her cheek.
Applejack just stared, she didn’t know what to think. She didn’t blame Twilight, at least not entirely. To face eternity alone is a terrifying thought when she stopped and thought about it. Celestia and Luna have each other, even the thousand years alone Celestia at least had the hope of Luna returning. But Applejack would have at least have been asked if it was ok. But what would she have decided if she was asked? She was as afraid of death as much as the next pony, but would it be right to just keep right on living when other ponies don’t get that opportunity? Suddenly she realized turning the offer down would be to abandon Twilight, she absolutely would have said yes.
Fluttershy just stroked Twilight’s mane trying to calm her down. Twilight sat passively letting Fluttershy calm her. Altho she was still worried, she felt a tremendous relief after finally getting it all off her chest. Discord turned back into himself, refraining from his usual antics.
“Did you know?” asked fluttershy.
“Yes, and there’s no way I can reverse it.”
“Well, I’m glad” Fluttershy said. “You won't ever have to be alone again.” Fluttershy’s gentle smile warmed Discord, Fluttershy then looked down to Twilight and said “ and neither will you, Twilight.” Twilight started to cry into Fluttershys chest.
When the time came to confess to Celestia, Discord again offered to take the blame, but Twilight again turned him down. She was however, convinced not to reveal that she acted without permission, rationalizing that if they had been asked they probably would have consented.
Twilight was scared, but this time her friends were by her side, and the words came much easier. At first Celestia was stern, explaining how disappointed she was that Twilight had done something so drastic without consulting her, but then her tone softened when she admitted she could understand why she had done it, and that deep down she was pleased that her and Luna now had a larger circle of friends. Her tone again became severe when she told them that their rolls as the defenders of Equestria was now permanent, and that commitment was their price for Immortality.
“What about me?” asked discord. “I was already Immortal.”
“Oh you. Defending Equestria is your price for freedom.” said Celestia in mock severity.
“Oh right, that.” Said Discord putting his fingers together pretending to be bashful. Twilight wondered if they were flirting. Luna rolled her eyes at the interaction which Twilight suspected meant that they were, thus Twilight quickly thanked Celestia for her understanding and quickly backed out of the room.