Suspicious
It continued for several weeks. Celestia would wake up, raise the sun, make Luna's breakfast, and head down to Star Swirl's library after Luna was asleep. The first few days were solely for research, but she started to make some progress after a little while. Star Swirl had written down everything he did in creating the mirror, so it was pretty easy to copy his work.
Of course, she had some royal duties to attend to very often, but she managed her time well. Unfortunately, it meant she needed to say no to something. Events such as charity concerts, balls, and even a Wonderbolts show had to go on without the princess.
Was her schedule this hectic back then? Celestia doubted it. Equestria had considerably less ponies when she first started her travels with Star Swirl.
After she had run into Luna, Celestia made sure that she kept track of time during her visits so that her little project would go unnoticed. Every time they ate together, Luna appeared not to suspect anything, but Celestia never knew when it came to her sister.
And Luna made sure that Celestia didn't suspect her of anything either.
Luna noticed the dust and dirt on Celestia's hooves when they ate dinner every night. Her sister spaced out every so often when Luna tried to make conversation. And three weeks after Celestia was caught using the secret exit, Luna saw her use the same passage from a little ways down the hall. She managed to duck into a side hallway just as Celestia looked around to make sure she wasn't being watched.
Something was going on, and Luna wasn't going to sit idly by while Celestia put Equestria, and her heart, in jeopardy. As soon as the moon was high in the sky that night, Luna sent a message to Spike.
Back in Ponyville, Twilight Sparkle slept soundly. In the next room, Spike was dreaming about a mountain of gems when he coughed. Then again. He opened his jaws for a giant belch of green fire and spat out a scroll.
Grumbling, Spike got to his feet and picked it up, but this one had the seal of the moon rather than the sun. He opened the scroll and blearily scanned it. Spike's green eyes shot open, and he scrambled to wake up Twilight.
An hour later, the rest of the Mane 6 was wide awake and on a train to Canterlot. They had the majority of the train to themselves, being the middle of the night, aside from a disgruntled stallion who glared at them from the corner of the train car.
"Twi," Rainbow asked, breaking the silence, "You're the egghead. What do you think happened to mirror Sombra? I faintly remember something about balance, and that's why that other Sombra's all evil now."
Twilight gulped. "Well, Princess Luna's theory is actually pretty likely."
"And what is that, exactly? We don't know very much. When you woke us up, you just said that Princess Celestia was experimenting on the mirror again, driven by the pain of seeing the Sombra here with Hope." Rarity yawned. "And this couldn't wait until morning?"
"It's obviously an emergency!" Pinkie yelled. "Remember last time, when we had to go through the mirror, and we saw the evil Celestia and Luna, and the line between the worlds blurred, just because Celestia messed with the portal over and over and over and over-"
"Pinkie's right, the results could be disastrous if the rift between the worlds reopens. Luna believes that to make up for Sombra's reformation, Celestia and Luna in the other world have to have flipped to the dark side, in addition to mirror Sombra." After Twilight said this, everyone in the train car with the exception of the stallion gasped.
Applejack frowned, putting a hoof to her face contemplatively. "So that means that while we're sittin' here with good princesses and good Sombra, those ponies are fightin' not one, but two evil forces? That ain't right."
"But AJ, these are alternate universes. There isn't a way to keep everything peaceful in both worlds. If everything is fine here, then there has to be chaos in the other world. That's just how it has to be."
Pinkie added, "And besides, the good ponies here are evil over there, so those ponies must be happy with the destructive world because, you know, everyone's evil and stuff."
The train screeched to a stop in the Canterlot station. Everyone got off and raced to Canterlot Castle to find Luna. She was waiting for them at the front gates.
"Thank goodness you've arrived. I need all…" Luna caught sight of Spike glaring at her from his perch on Twilight's back, "seven of you to help me with Celestia. I don't know how close she is to completing the new mirror, but I think she started sometime after the events in the Crystal Empire. It's imperative that we find out exactly what she's doing before her reckless actions take a toll on us all."
"You can count on us, Princess. What do you need us to do?" Twilight asked.
"The six of you successfully navigated the library before, so I need you to go down to look at her research. The dragon and I will take care of matters from up here."
As Twilight and her friends ran to the library, Spike gave Luna a look. "How come I always have to stay here with you while the ponies go have fun adventuring?"
"Last time, it was simply for my entertainment while they're gone. This time I need your assistance with the most important task."
"Really?" Spike's eyes shone with excitement. "What is it?"
"We need to operate undetected by Celestia. I need you to stand outside the hallway to her chambers and let me know immediately if she leaves them."
"That's boring. Not going to lie, I expected something better that couldn't have been done by a palace guard."
"We don't know who will tell Celestia of our actions, so I need someone I can trust."
Luna looked at Spike pleadingly. Rolling his eyes, he said, "Fine. I'll let you know when she wakes up."
"Thank you, Spike. Even the littlest actions can make a big difference." With that, she flew off into the night.
Thank you to those who reviewed!
Starkvb - Thank you for your interest! And I completely agree, part of the reason I decided to write this was because I can rarely find any fanfiction that has to do with any of the IDW comics.
Thanks for reading! Please comment if you have any questions or feedback.