Deep within the castle, there were two guards watching the mirror room. As they remained vigilant, one guard said,

“You know, Princess Luna has been gone for several days now.”

“Yeah. It’s almost like she disappeared. Just what is in that room?”

“Beats the hell out of me. At this rate, we’d just be sitting out on the invasion when those creatures get us.”

“Right? We’d just be street food if we ran into any of those vile monsters out there.”

“How right you are.” a female voice called out.

The guards prepared their spears at the ready. They were shaking with anticipation of their deaths as they waited for the figure to emerge. Just then, they see a hoof emerge from the shadows. When the figure emerged, they were shocked to learned that it was the late Princess Celestia.

“Y-Your Highness?!” the guard on the right shouted.

“H-How?!” the guard on the left shouted as well.

“Indeed. You two seem to have plenty of questions, but now is not the time to play catch-up. I am searching for my sister and I was hoping that she was inside this room.”

“Y-Yes, but-”

“But? I thought I was the Ruler of Equestria?” Princess Celestia said in a taunting manner.

“W-We don’t doubt you’re on our side, Your Majesty. But how can we-”

Just then, the temperature in the room started rising. The guards started sweating as Princess Celestia grabbed them by their throats with her magic.

“How can we be certain? Equestria really has fallen.” Daybreaker said in a dry tone.

Turning herself back into Daybreaker, she threw them through the doors and surrounded them with flames, incinerating them in the process. Moving inside the room, she looked around and saw a broken mirror with shards all over the place.

“You really thought ahead, didn’t you Spike?” Daybreaker taunted as she gathered the shards.

Putting the mirror back together one piece at a time, the glass started forming together as each fragment made contact. Having reassembled the entire mirror, it started to glow really bright, even temporarily blinding Daybreaker in the process. But after the glowing started to cease, the mirror was floating and it was as if nopony has ever touched it.

“Won’t my dear sister be surprised.” Daybreaker said, approaching the mirror.

Upon entering the mirror, it became black. There was nothing in sight. But all Daybreaker could do was glow her horn and search for her missing sister. Looking everywhere from top to bottom inside the mirror world, Daybreaker couldn’t find her. Even the faintest bit of magic had misled her and got herself lost.

“She has to be here somewhere. Even Discord wasn’t this hard to find when he came close to conquering Equestria. But after what he did, he is no more but a footnote in our glory as the Princesses of Equestria. And my soon-to-be glorious new empire.”

Daybreaker continued her search for Nightmare Moon and she eventually stumbled across a bit of black ooze on the ground.

“This is the same corruptive substance that Twilight smuggled into the Crystal Empire. She never was the relenting type when it came to research.”

Just then, the ooze shrieked and proceeded to attack Daybreaker. But before it could land a hit, it was suddenly grabbed by Celestia. It tried desperately to escape, but to no avail.

“You seem to be in a hurry. So am I. Maybe you can take me to my sister.”

However, the ooze ignored her and tried escaping Daybreaker. She was angered and confused by this. She was seeking answers for the whereabouts of her sister, yet she receives no reply. But just then, she noticed something. The more closer she got, the more the ooze wanted to escape from Daybreaker. The latter took notice of her flames on her head. Igniting one from her hoof, she moved it closer towards the ooze, making the corruption panic in the process. Just then, Daybreaker had a realization.

“I see. Since you’re afraid of my flames, you try to elude me. But it appears you wish to make your way back to the source. You will take me to my sister.” Daybreaker said, looking at the ooze.

Following the direction of the ooze, Daybreaker slowly started making her way towards the direction of Nightmare Moon.

***

Three hours have passed since Daybreaker followed the direction of the fleeing ooze. Just as she starting to get nowhere, she suddenly heard clashing from the distance.

“Sister?” Daybreaker said, flying towards the source.

Making it closer, she noticed Nightmare Moon. Firing shot after shot at the rubble before her, Nightmare Moon was extremely angry in the predicament she was placed under. But delighted with the joy at seeing her well, Daybreaker shouted,

“SISTER!!!”

Suddenly hearing a voice that she would never imagine hearing again, Nightmare Moon said,

“Sister?”

She turned around and saw the source of the flames in the distance. Shocked by this, Nightmare Moon flew closer to the source of those flames. Upon getting closer, she was shocked to see that those flames belong to her sister.

“S-Sister?” Nightmare Moon said, moving closer to touch her cheeks.

Upon feeling them, her feelings of suspicions were correct. Her sister has returned from the dead.

“SISTER!!! You have returned!!! But how?” Nightmare Moon asked out of curiosity.

“Ask the two-faced Princess of Friendship. I was only able to return because she was desperate enough to raise me from the dead. And this little thing led me to you.”

“Indeed, she was. The creature must’ve lost a bit of itself once it escaped. But what has happened to you? You’re mane was the color of a rainbow and now you look like you have a campfire on your head.”

“You’re one to talk with a depressing feel to your appearance.”

“How dare you!!! I am the Princess of the Moon!!! But soon-to-be the Empress of Equestria.”

“So it appears we now have a common goal.”

“Yes, we do. I am looking forward to seeing the expression on that lizard’s face when we return to Equestria.”

“It will be even more hysterical when I melt him into wax. But right now, we need to leave this gloomy world.”

“Why not? I think it suits me since I appear to be depressing.”

“You know I jest, sister. Just think about killing the ungrateful little gecko who manipulated us into thinking he was dead.”

Smirking at the idea of it, Nightmare Moon said,

“Lead the way, dear sister.”

Hearing this, Daybreaker went back towards the exit with Nightmare Moon following suit. After exiting the mirror, Nightmare Moon asked,

“What should we do with everypony else once the Crystal Empire has fallen?”

“We will build an army. With the forces of Equestria and this new power on our side, not even the Corruption will stand a chance. We will return here once this domain has fallen. Are you interested?”

“As if you needed to ask.”

Hearing this, Daybreaker and Nightmare Moon teleported away from the Crystal Empire, disappearing into Shadow Equestria.