This story is a sequel to What do Nightmares dream of?

Nightmare Moon is caught in Celestia’s bedroom, where she is confronted by the two princesses and opens up completely to them.
She tells them that she has changed, and her feelings are the complete opposite to what they used to be. Especially her feelings towards the Princess of the Sun.

Cover art from Vector-Brony’s deviantart

Nightmare Moon has spent years of accumulating enough magic for herself to materialize after her defeat by the Element Bearers. She is separate from Luna. Her own being. She does not want eternal night anymore, having realized it would doom Equestria.
She can only think of the Sun. Of how dear is the Sun for her actually. She wouldn't take it from the skies... Everything needs her.
Even dark creatures as herself.

Cover from 90sigma's DeviantART

EDIT: Wow. Featured. I didn't expect that. You guys are wonderful. There will DEFINITELY be a sequel to this now.

This story is a sequel to Princess Luna is dead. Again.

He really should have known better. Saying that he didn't like Princess Luna, even if she could no longer hear him, would have probably lost him the sympathy of many ponies in Canterlot, and it had been perhaps a rash decision for an expert diplomat like him. Still, the damage would not have been irreparable. But how was he supposed to know that she was still alive? Clearly, jumping out of the window had been the only logical course of action after that.

Princess Celestia was sure that the day was going to be great. The Sun shone bright in the sky, the birds were singing, and nothing could possibly go wrong. That was, until she received some rather grim news concerning her sister.

She thought she'd been clear enough about things last time.

Polish translation by Dolar84.
Spanish translation by SPANIARD KIWI.
Audio reading by Pony&Wolf Productions.

After being sold a "magical" necklace from Trixie, Queen Chrysalis believes she is completely invisible, and begins systematically ruining the lives of Twilight Sparkle and everyone around her.

Sadly, Chrysalis is not invisible. Not even close.

Artwork by Ernestboy.

Celestia thought she knew her sister. She was sure that nothing could surprise her anymore. She was certain that there was nothing more that Luna could possibly be hiding from her.
One attempt to identify a changeling presence in the royal guard later, she was coming to terms with how reality had decided to prove her wrong.

Audio reading by Pony&Wolf Productions.

During her engagement to Shining Armor Princess Cadance makes a new friend, the pegasus businessmare Chrysanthemum Crown. Beautiful, confident, and full of surprises, the two strike up a rapport that brings light to both their lives.

During the preparation for the Invasion of Canterlot, Queen Chrysalis finds herself deep in the good graces of the pony Princess she will replace. And the more she gets to know her, the more she understands why Cadance is the Princess of Love.

Third Place Winner in the Dear Love: A Beautiful Discord Contest
Cover Art by Lopoddity

Nightmare Moon has been defeated, the long-lost Princess Luna has returned, and everyone is happy. Well, Princess Celestia is. The castle staff is still rather unnerved by everything the sudden disappearance of their monarch, and are still wary of this situation.

One guard is particularly unhappy with this new arrival. Which is why he's staying as close to her as possible.

Sunburst has a sudden realization about Starlight’s age-reversal spell.

It turns out, the changeling invasion of Canterlot was very...improvised.