Twilight Spark was dying. The thought bounced around in Rainbow's head like a tennis ball in a cotton candy machine. One of her best friends, the mare she had fallen in love with over the objections of nearly every other pony she knew, was dying.
The worst part was, there was nothing she could do. She sat there in the hospital, her love hooked up to machines that monitored any number of bodily functions that Dash couldn't be bothered to understand. The only one that mattered to her was the one showing the steady beat of her marefriend's heart. As long as that one kept going, she could keep going.
Somepony could look into the room and see the rainbow-mane laying on the chest of the unicorn laying in the bed, and see that visiting hours didn't apply here. The pegasus never left Twilight's side unless it was to use the bathroom. She slept, ate, and read books aloud right in that chair.
Their other friends visited of course, in those few hours a day that Twilight was able to wake up enough to be coherent. She spent most of her time listening to her friends tell her how things were out in Ponyville, how Spike was handling the library by himself like a grown-up. Rarity had just come up with a new Spring fashion line that was already the talk of the industry all the way in Manehattan. They smiled and laughed as if nothing was wrong, planning for coming Galas and Pinkie's parties. Nopony touched on the subject of why she was laying there, barely able to hold her head up off the pillow to eat the small meal she could keep down.
Every doctor and specialist in Equestria had been called in to find out what was wrong with the personal student of Princess Celestia and the bearer of the Element of Magic. None of them could come up with a reason why she was simply fading away. Her magic font was as strong as ever, if not stronger, but her body simply could not continue working on its own.
She had stayed at home at first, Rainbow taking care of her with Spike's help until it had become impossible for her to stay out of the hospital. Now, she was a hollow shell of a pony, weak and thin.
Rainbow was in the middle of the latest Daring Do, regaling Twilight with the tale of the famous fictional adventurer as the unicorn lay there with a weak smile and tired eyes. She enjoyed listening to her marefriend read and the fact that she had stayed at her side only made her love the pegasus more.
Applejack entered the room with a smile, hiding her sadness well. She'd gotten better at that, Twilight noticed.
"Ah brought y'all some apple fritters, girls. Ah know they're one o' the few things ya can still stomach, Twi."
Rainbow and Twilight both nodded, "Thanks, A.J.," the unicorn said, forcing herself to sit up a little higher on the mound of pillows that currently propped her up. Dash immediately leaped into action and assisted the frail mare as Applejack brought the bag over to the bed.
"How ya feelin', Twilight?" the farmer asked with that fake smile. She had gotten way too good at that.
"Oh, just great. Every time I try to pick something up, my head explodes," she said, referring to her failed efforts to eat with her magic.
Applejack's smile turned to a frown and she looked over the two, "Oh, Ah also have a message from Celestia. She says she may have found somethin' that could help and will be by later to talk it over with you both."
"Both of us?" Twilight asked, looking at her marefriend, who was nibbling on a pastry.
"Ah don't know the details, Twi. Just that R.D. needs ta be here too."
"I'm never leaving her side, you know that, A.J."
"Ah know, sugarcube. Ah was just passin' the message," she said before giving them both an affectionate nuzzle and taking her leave.
Twilight managed to stay awake until the Princess' arrival, stunned by the arrival of Luna as well, "Princess Celestia! Luna! I've missed you both!"
"As have we, Twilight Sparkle," spoke the night princess.
"Twilight, Rainbow, it's good to see you both. I was deep in the library archives when... When I came across a spell that I believe may help..."
"Princess?! Really!?" Rainbow Dash said, leaping up out of her chair and looking perkier than she had in months.
"That's why I wanted you both to be here. It is a dangerous spell and is, in fact, forbidden magic from the time of Nightmare Moon."
"Indeed. Twilight Sparkle... I will have to become that again, only briefly. I know I can come back this time, but I will need her dark powers."
"Luna? No, you can't..." whispered the unicorn.
"I am willing to do so for one of my best friends, and the pony who saved me from her in the first place, but I must warn you both. This spell was not originally intended to save lives."
"No, Rainbow Dash, it was meant to end them. See, when I... When Nightmare Moon wished to torture a pony in a particularly inventive way, she would cast this spell on something particularly fragile or short-lived, like a mayfly or similar. In doing so, it would link their life-forces. When the fly perished, either from being swatted or from time, so too would the pony. They would also age at the same rate as their linked creature, rapidly becoming ancient ponies in less than a day."
"That sounds... incredibly wrong..." Twilight said.
"Yes, Twilight. It was. However, now that my sister has rediscovered this spell for me, I believe I can make use of it to save your life by linking it to Rainbow Dash's, that is, if she is."
Before Luna could finish the sentence, Dash stood up straight and stared straight into Twilight's eyes, "Do it."
"No buts, Twilight. I love you. I wanted to be with you forever. If linking my life force to yours can keep you alive for longer... Call me selfish, but I don't give a buck."
"Dashie!" Twilight said, shocked at the language.
"Princess Luna... Do it."
"As you wish. Sister, if you would kindly stand back and be ready to put me down if I should lose control?"
"Of course Luna..." Celestia said with a frown, standing back and charging a spell of her own.
Luna's transformation was quick. In no time at all, Nightmare Moon stood in the hospital room with a smile, "Ah, such power. Tis good! Now, to cast this spell..." she said with a smirk, horn glowing.
Twilight and Rainbow Dash felt themselves drawn close together, hearts tugged to become one. With a smile, the looked back to Luna, who sealed her old self away carefully, then frowned.
"Oh no... My dearest friends, I am so sorry. For just an instance, Nightmare Moon took control... and flipped the spell."
"You don't mean?" Twilight said, horror growing on her face.
"I'm afraid so... Instead of you living for as long as Rainbow Dash... She will only live as long as you."
"It doesn't matter," Rainbow said, looking at her marefriend and giving her a kiss, "I wouldn't want to live without you anyway, Twilight."
The two shared an embrace as Rainbow's body rapidly began to lose strength until she collapsed next to her lover, "Oh, Rainbow..."
The two princesses quietly took their leave from the room as the two lay together in the bed.
"Twilight... These past few years have been the most awesome of my life... and I'm glad I could spend them with you."
"Dashie... I... don't know what to say... You can call Luna back, have her undo the spell!"
"No way, Twi. I couldn't live without you even without us being linked. We were meant to be together forever, one way or another."
"But... Dashie, I..." the unicorn was about to voice another objection but was interrupted by another kiss from her marefriend.
"But nothing, Sparkles. We're going to be together. That's all that matters..."
The two shared their embrace as the night came. Sometime in the night, while they slept in each others hooves, the monitor that Rainbow Dash had kept such a close watch on began to slow and finally, as dawn came, it stopped, taking with it two ponies who had been destined to be together since they were fillies.
I'm sorry about this, I really am. It was hard to write, but I had to get it out of my head. Now, if you'll excuse me, I'm going to cry out the rest of these tears and wait for the hate mail.