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)

This story is a sequel to Princess Celestia: The Changeling Queen

This story is a direct sequel to Princess Celestia: The Changeling Queen. Reading that first is necessary to understand any part of this story.

Co-authored by vren55 and Zervziel

Alternia, sister to Chrysalis, ruled Equestria for a thousand years, disguised as Princess Celestia, while the alicorn slumbered in a healing sleep. Now revealed, Alternia prepares to become Equestria’s first changeling princess, and prove herself to the ponies she loves at the side of her co-rulers Luna and the newly-returned Celestia.

But even as the crown descends onto Alternia’s head, something is stirring in the depths of the Eastern Sea, something that will turn the surface world onto its head. Some power that could destroy Alternia, and all that she loves, before she can even regain the approval of her own ponies.

Will Alternia restore the trust her ponies once placed with her? Will she found a hive? Will she find love?

All that is certain is that Equestria, and the world, will never be the same again.

Now with a TV Tropes page.

Empress Tethys and the Kelpies Created by Zervziel

That Fantastic Cover art is by Plainoasis

Pre-read and edited by:
Blankscape,
FinalFan,
Courage Fire
Cosmic Cowboy