"Take my hand, Twilight. Let me show you that there's another way... just like someone once did for me."
Twilight looked at Sunset, tears brimming in her eyes. She opened her mouth and spoke.
"Yes... but I have to do something else first."
Sunset looked warily at Twilight, wondering if the magic that the other girl was currently holding was beginning to overwhelm her again. "And what is that, precisely?"
Twilight looked at Sunset. "You truly don't know?"
Sunset shook her head, her hair drifting weightlessly in the void. "No, I don't know. What do you need to do?"
Twilight gestured with her hands at the magical void surrounding them. "Can't you feel it? The sense of wrongness about all of this?"
Sunset opened her mouth to reply, then paused. Beneath the feeling of harmony singing through her veins, there was something else, something that she had felt every time that she had walked past Discord's statue in the Canterlot Gardens. A sense of a torrent of barely restrained chaos.
Twilight resumed, snapping Sunset's attention back to her. "Don't you see? The magic is causing problems because it doesn't belong here. This isn't its world. This universe is not built with a place in the framework for magic. That is why it keeps changing, keeps mutating, because it's trying to find its place, and the universe keeps rejecting it."
Sunset thought of the past, of how the magic had began, how it had changed from just magic to music-triggered when the Sirens showed up, and then to being rooted in demonstration of their elements during the past few days.
Twilight continued. "And if it doesn't find a home, then it will continue to slowly tear apart the fabric of this universe, until finally the universe reaches a point where one too many tears is formed, and the fabric of space-time will be so weakened that the tear will continue until everything ceases to exist."
Sunset relaxed.
Just a fraction, true, but it didn't seem like Twilight was being power-crazed.
At the moment, at any rate.
"So what do you propose to do about it?" she asked.
"There's two options. Option one is that I attempt to send all the magic in the human world back into Equestria. That probably would have worked before I tore a number of portals into Equestria. There's no way to know how much magic came through, or where it went, so if I missed any, it would be permanently trapped here and we would have the same problem as before."
Sunset nodded slightly. "And option two?"
Twilight looked at Sunset with determination in her eyes. "Option two is that I integrate magic into the fabric of this universe."
Sunset's jaw dropped. "Do you even begin to realize the magnitude of what you just said??!!"
Twilight nodded. "Yes, I do. It seems impossible, but I think that I've figured out the way to do it."
"And that is??"
"I'll utilize you and anyone else from Equestria as a conduit. It'll first integrate itself within you, then anyone who has used magic in this world. Then it will spread to everyone else on this world, then gush out into the cosmos in an endless torrent."
Sunset hesitated. "Are you sure this will actually work?"
"As certain as anyone with limited knowledge can be", Twilight replied.
Sunset thought deeply about the integration of magic with the human world. It would cause chaos, problems, and confusion. But it would also prevent this universe from being destroyed.
"Alright, go ahead." Why do I feel like I'm overlooking something?
Twilight channeled magic, a portal to elsewhere opening. As she studied how magic was integrated in Equestria, Sunset suddenly realized what she had forgotten.
Anyone from Equestria?? Oh crap.
Sunset rocketed out, flying blindingly fast. She could sense the magic that Twilight was studying, and knew that she didn't have much time.
She reached out with her magic, searching for three voids that once were filled, but now were bone-dry.
She found them, and, summoning a cup-shaped shield, dove.
The Sirens were caught completely by surprise.
They were sitting in an alleyway, bickering with each other, when a golden sphere suddenly enveloped them. Before they could even blink, the shield turned solid and impermeable to physical objects.
They began to pound on the shield and screamed loud and long.
But no one could hear them.
Sunset grimaced as she felt a torrent of magic pouring through her. The magic that was attempting to fill the Sirens, blocked by her, flowed into her instead, then attempted to flow to the Sirens once more, which she had to block yet again.
Sunset screamed as the magic, flowing far faster into her then it could leave, ran out of space in Sunset's body.
It first flowed into her incorporeal wings, which quickly transmuted itself into flesh.
Then it spiraled into the horn, making it real and solid.
Then it was out of space once more, and Sunset attempted to hold on to her focus even as she screamed in terrifying, near-unimaginable agony.
And her body began to change once more.
Rainbow Dash, Pinkie Pie, Applejack, Fluttershy and Rarity were the first to transform, their half-pony forms returning.
Then everyone else began to do so as well. Principal Celestia, Vice-Principal Luna, and Dean of Academics Cadance gained both horn and wings. Flash Sentry got wings, while Trixie had a horn emerge.
The shockwave raced across the planet, leaving no human untouched.
Then it plowed through the cosmos at the speed of light.
Sunset couldn't take it anymore.
She howled, and her eyes went a pure, radiant white. She reached out in her agony, found the sphere that she had trapped the Sirens in, and tore a hole into another reality, thrusting the sphere through and then sealing the rift to the point that that patch of reality was rewoven even more strongly than before.
Then there was a brilliant flash of light, and Sunset was gone.
She awakened to her friend's anxious faces. They were all in half-pony form.
Sunset got to her feet, noticing with startlement that she now was three heads taller than her friends. She heard a rustling of feathers, and, looking behind her, she discovered that she had a massive pair of wings, and a large horn on her head.
She shook her head wryly. "Next time, remind me to ask Twilight what the side effects are going to be before she changes the fabric of reality."