by Europa
When she'd first become an alicorn, she wasn't immortal. She was like Cadance, with her physical mane and regular lifespan.
At first, she was not too worried about Chrysalis outliving her. Her workerfriend was nothing if not tough, after all.
Then the spirit of Starswirl emerged, and all her friends and her love tried to combat him, but what he lacked in power he more than made up for with experience and intellect. In the end, it had been Twilight on her own, facing down the isolation-maddened ghost. It was no battle of magic, but a battle of wits, and against all odds she prevailed and became immortal in the process, her mane and tail turning into a flowing rainbow of the colors of harmony, shifting from loyalty red to generosity purple and on and on.
Forever. She was going to live forever. Or at least, damn near close enough. With that thought in her mind, she summoned her courage and wed Chrysalis, putting their nations' history as enemies behind them forever.
With that done, life settled into a smooth monotony. World-ending threats stopped, and for the first time since moving to Ponyville Twilight's life was somewhat resembling normal. And so it continued... for a very long time.
They had a son, a thousand years after Luna's return. There hadn't been any point in rushing, they could both wait. It wasn't a halfling either, but rather a pureblooded changeling by some bizarre quirk of Chryssy's genetics. They named him Moonlit Web. He went on to become an architect, would you believe it?
Changeling history went back far, uninterrupted by Discord, and apparently ponykind was once incredibly advanced. Slowly, they returned to that level. With phones, internet, even space travel. When Kneeling Arms took his first step on the moon, fifteen hundred years after Luna returned, Princess Luna cried like a foal.
Things picked up after that. Tirek returned once more, allied with Grogar, and drained the magical power driving their technologies while the ram raised an army of the dead. In the end, Twilight fought Tirek to another standstill, long enough for her wife to hypnotize Grogar and send him after Tirek. Both demons died that day.
Time passed on, and on, and on. Nations grew and nations absorbed each other. Relations between species grew better and better. Eventually the URP - Unified Races of the Planet - formed, with Luna - Celestia had abdicated a while ago - Cadance, Emberbeak, Chrysalis, and many others on the highest level of its government. And then, with the world united, they turned their gaze up, and up, and up.
Eternal time passed as they slowly spread through the solar system, through the stars, through the galaxy, absorbing new species and allying with others. She and Chrysalis had long ago entered a dual-hypnosis pact, so that their love for each other wouldn't fade with time. Unethical? Maybe. At the time - and after - it seemed like a good idea.
Time passed in dizzy waves. Eventually the URP fell and Chrysalis, in a fit of rage, left the galactic group with her changelings to found a new empire, and Twilight went with her.
She'd left all her friends and family for Chrysalis. She never could say for certain if it was worth it.
And that was how she and Chrysalis found themselves, a billion years old, facing a random red giant from a ship. A billion? Damn, she was old.
"It's nice, isn't it?" she asked, leaning into Chryssy.
"Mmhmm," said the changeling. Chrysalis rested her head on top of Twilight's, no doubt feeling her ethereal mane massaging the bottom of her chin. "Do you ever regret coming with me?"
She sighed. "Sometimes. It's Celestia, Luna, Cadance, Discord. They're my friends, and I love them."
"But not as much as me?"
Twilight couldn't help but smile. "Not as much as you. So, what're your plans for this supercluster?"
"I'm not sure. Maybe enslave its populace, maybe send them over to... back there."
She poked her side. "Chryssy, no enslaving the indigenous population!"
The former-and-again queen pouted. "You never let me have any fun."
"If you want to conquer a people, do it in virtual reality."
"But it's not the same if they aren't real!"
"Then make it so you think they are," she suggested.
"Alright." They sat and kept watching the red giant swell, its apocalyptic light scouring its solar system of life, dimmed by their ship's screens. It was almost poetic, for Twilight to watch a dying sun with her wife. Not to say that Celestia was unwell, but her presence in her life had been waning for a long, long time.
She looked forward to the eternity ahead.