This is a one-shot I wrote back in 2016 about Celestia recieving a prophecy about her sister. Keep in mind that this is unedited, aside from a few corrections, so it may not be completely accurate concerning newer episodes. Anyway, this is a fanfiction so I guess it's ok. :))

After the banishment of the sinister Nightmare Moon, Equestria has countered a state of peace. Civilians went on with their normal duties. Farmers cared for the land, promising a good harvest for their families. Weather ponies kept the weather balanced, and unicorns casted spells as a friendly help for their earth pony neighbors.

Almost 100 years have gone by. Now, the battle of the sisters was just a story told by grandparents to their little ones.

Seasons and seasons passed. For Celestia, the princess who raised and lowered the sun and moon, years and years of regret.

The lithe figure of the alicorn princess floated up a grassy hill, not far from the ruins of the Castle of the Two Sisters. Her silhouette was outlined against a tawny sunset, painted with bright pink and golden light.

Celestia's head lowered as she landed on the furry blanket of green. Standing upright on the feather-like grass, she raised her muzzle towards the sky with a somber face. Her horn illuminated with magic. The still sun started to move, sinking lower in the sky. After a while it disappeared below the horizon, and the bright fusion of warm colors was replaced by an expanse of dark purple, speckled with stars.

Celestia's golden magic then faded, and brightened again, but this time with a blue hue. The moon rose into the night sky, with the same outline of the Nightmare Moon embedded against the bright background of it, reminding Celestia of what happened years ago.

"The 'Mare in the Moon' as they call her." Celestia sighed, and the magic disappeared. Each night was always the same: Celestia would lower the sun, raise the moon. She would gaze up at the glittering orb — her sister — with remorse. Celestia knew that she had to banish her sister. It had to be done. For the ponies, for Equestria, for everypony's sake.

But it still broke her heart
that she had to lose Luna..

Celestia closed her weary eyes, exhausted. After what seemed to be a few hours, Celestia perked her ears when she heard hoofsteps approaching. Blinking her eyes open, she realized the sky was darker, with more tiny stars twinkling from above.

The pony staggered up the hill, but he was still most confident with his every step. He was a unicorn, with a long white beard. His amber eyes reflected wisdom, and Celestia brightened.

"Star Swirl the Bearded! It's nice to see you.." Celestia greeted with a friendly wave of a hoof.

Respectfully, Star Swirl dipped his head. "It's always a pleasure seeing you, Princess Celestia."

Celestia heaved herself to her hooves. "Did you need to discuss anything of the sort with me?"

He shook his wrinkled head. "No. I just wanted to make sure everything was running smooth—" Star Swirl's words were cut off abruptly as a flaming comet streaked past overhead. It shook the earth with a powerful force, before silence returned.

Star Swirl stared at the sky, his eyes widened to two amber moons of curiousity. Celestia flicked her gaze back to the wise old unicorn.

"What do you suppose that was?" Celestia wondered, slightly concerned.

Star Swirl looked back to Celestia. He dropped his gaze to the ground with a somber look. "It's a prophecy."

Celestia tilted her head, her flowing mane doing the same. "...What prophecy?"

Star Swirl sighed, and Celestia could hear weariness in his voice, which cracked with age. "The Stars will aid in her escape."

"The stars?" Celestia pondered. "It doesn't make sense! In her escape..." She turned to gaze at the risen moon. "Could it mean that my sister might return?"

Star Swirl the Bearded gave her a warning glance. "If it's true, Nightmare Moon will return. Your real sister seems to be ... gone."

Celestia sighed, her cracked heart feeling heavy in her chest. "I guess after so many years I'm just wishing for that to not be true."

Star Swirl nodded. "I will do my best to decipher the omen."

The old, but experienced unicorn turned to trot down the hill. He turned his head. "Take care, Celestia." And he disappeared into the darkness, leaving Celestia weighted down by her own doubts and concerns.

She lifted her head once more to the shimmery moon. "My dearest sister, you shall not be trapped there forever. For perhaps the stars will aid in your escape."

Celestia trotted back down the hill. She glanced back, tears pricking at the edges of her eyes.

"And bring you home, my sister."