Well it's not actually a sequel. Here is a collection of short stories and histories detailing the life of Alternia, a changeling queen impersonating the life of Princess Celestia. These are the stories of the ruler under her mask.

Reading the main story: Princess Celestia: The Changeling Queen is a requirement if you don't want to be spoiled or confused. I will try to provide background information when I can.

For readers of the main story, there are basically no spoilers if you've read past chapter 8. Enjoy!

This story is a sequel to Princess Celestia The Changeling Queen: Stories Behind the Mask

At the Royal Wedding, Chrysalis and the Changelings were revealed to all of Equestria.

But another mask was torn away that day. A mask born for a thousand years. A mask created on one promise. A mask, that has become synonymous, fused, to its bearer.

A mask that when ripped off, causes Twilight, her friends and Luna to question everything they ever knew about the one pony, one very important pony.

At the Royal Wedding, the meaning of the phrase 'Princess Celestia' changes forever.

NOTE: Chrysalis is NOT Celestia!!! That'd be impossible to pull off.

Credits to: Plainoasis for the design of the cover art
Note 2: Original cover art here: https://angelea-phoenix.deviantart.com/art/Contest-entry-Changeling-Celestia-337023552

Pre-read/edited by Zervziel,
Blankscape,
FinalFan,
Courage Fire
Aurora Borealis

Side Stories to this can be found: here.

An audio-reading on youtube up to Chapter 21 is up by StraightToThePoint Studios. I'm aware there are others but this is the nearest complete one: [embed]https://youtu.be/X3eMW673CSY[/embed]

There are also 2 print versions of Princess Celestia:The Changeling Queen. Nonexistent Publications run and Ministry of Image's run.

Contribute to the TV Tropes Page (thanks to Babs_Seed72 for getting it up)

Nightmare Moon may be stuck in the Celestial prison but that doesn't mean that she won't be rehabilitated. After all she needs to be civil with her Co-Regent doesn't she? But how can she and Celestia be civil if they are millions of meters apart. Simple, letters.

Edited by Zodiac
Preread by Jumbled

Luna, princess of the night, is in her bedchambers, ready to go to bed for the next night. She lays on her bed, wondering, what if I was the eldest sister? What if Tia was banished to the sun? What if I ruled all?
Celestia, princess of the sun, is at Twilight Sparkle's new castle, helping her set up her new library. She uses her magic to teleport a book, labeled, "Alternate." She opens it to find a spell to switch her sisters' duties. Without thinking, she takes it home, only to see that she is the younger sister.