King Sombra goes to Canterlot.

Princess Luna fills her thoughts with him.

Celestia hates Sombra due to being embarrassed in front of him and because he
paid more attention to Luna.

But if Luna fell in love with Sombra... What would happen if Celestia found out?

Takes place (potentially) in the same continuity as Highfire's Great Big Mailventure.

Princess Luna is presumed dead. Her sister weeps. Her friends mourn. A nation searches.
This is not their story. Not entirely, anyways.
Instead, this is the story of what happens, when she returns.

Updates whenever I feel like I have something solid.

Everything got so much worse for batponies after Nightmare Moon was banished. Even those with no involvement in the war, Equestria turned hostile. Instead of a loving home, Mira grew up as an orphan, cowering in terror from the advance of Princess Celestia's Golden Army.

In the shadowy caverns of Understory, the ancient arts were still taught: Dreamwalking, and all the 'dark' practices that were once fundamental to the bats' reverence of Princess Luna.

After the death of somepony close to her, Mira finally resolved to do something. She didn't have the power to fight against Equestria, but maybe she could do something else.

With the forbidden knowledge of the sleeping world, she could rescue Nightmare Moon, and save batponies everywhere from extinction. That, or die trying.

Updates Wednesdays.

Originally written as a Patreon reward for TyrannisUmbra on my Patreon.
Editing by Two Bit and Sparktail. Cover by Skydreams.

AU. Based on the first season. Twilight and Celestia begin to drift apart due to a misunderstanding. Will Luna speak up and repair the breach, or will she remain silent to keep her new friend, Twilight, all to herself? What other challenges will face everypony involved because of this new relationship?

It's a simple little love story. Unfortunately, love's not simple.

Luna never liked it when ponies just slept right through the night, not giving a thought to her hard work. Even her own sister, Celestia, ignored her for royal duties. It drove her jealousy, and it caused her to become Nightmare Moon. Now, a thousand years later, she is back. Celestia decides to throw royal to the side for once, and watch as her sister raises the moon and paints the night sky.

Inspired by the beautiful animation: Do you want to see the moon rise? by EileMontyDubz.

Also, for a wonderful take on how Twilight might've viewed the night sky after Princess Luna's return, go read I thought I knew the sky by nightwalker

On the night before Hearth's Warming Eve, as she slumbered peacefully in her warm bed, Celestia found her dreams interrupted by her younger sibling, who comes to her chambers with an idea in mind.

Artwork by the person on the other end of this link to the image.
http://mlpforums.com/uploads/post_images/img-2102581-2-187951__safe_princess+luna_princess+celestia_snow_snowball_snowball+fight_artist-colon-centchi.png

Written for the 'Celestia and Luna December Fanfiction' writing contest.

POPULAR SECTION - 19th December, Friday, 2012. Again? You all must really like me! I love you all! Especially the, ah, lovely ladies among you...wink, wink. XD Merry Christmas to you all!

Luna has returned to Celestia's side, but Luna would rather lounge about the castle than return to her old job as co-ruler.

This fic was featured on Equestria Daily on July 4, 2011 (well before Luna Eclipsed).

This story is a sequel to Smoothing the Knots

Princesses Celestia and Luna take tea under less than ideal circumstances: house arrest for psychiatric care following Luna's revelation about the her use of the Tantabus to torture herself.

Ever the thoughtful sister, Celestia tries to help Luna open up about her addiction to guilt and suffering in order to understand why Luna isn't happy now that the pain has finally left her. But Luna has a very different topic she wishes to discuss.

Ponies all over Equestria rejoiced over the defeat of Nightmare Moon. These ponies had no idea about the cost it took to grant them this peace. Princess Celestia had to seal her own beloved sister, Luna, away on the moon. For the first time she is going to have to raise her sister's moon. She wonders if there had been something she could've done to prevent her sister's descent into darkness.

Siren daughter of Sombra, Shadow Fall wants to have a normal life and explore the world. So she escapes her father's castle and becomes the awesome Rainbow Dash. Soon she and her new friends are battle villains together, including Sombra.