On this very night, Twilight Sparkle of Ponyville had just become an alicorn after having helped restore her friends' cutie marks and who they are. Princess Celestia had arranged for her coronation tomorrow morning at the Crystal Empire and Princess Cadance had invited Twilight and her friends to spend the night over at her and Shining Armor's palace. The Man 6 had just then arrived at the palace where the three other alicorns are waiting for them. Everypony was practically excited for Twilight's coronation into becoming a princess tomorrow, including Twilight herself.
"Hoo-wee! Your very own princess coronation tomorrow. You must be over the moon, Twilight." Applejack said to Twilight.
"Ooo, I am excited." Twilight replied to Applejack. "But, to be honest, I'm a little nervous, too."
"You're nervicited." Pinkie Pie told Twilight before bouncing up and down repeatedly. "It's like when you want to jump up and yell 'Yay, me!'. But you also want to curl up in a teeny-tiny ball and hide at the same time." As Pinkie said that last part, she did exactly that. "We've all been there!"
"I'm there almost every day." Fluttershy said to herself disappointedly.
"You've got no reason to fret, Twilight." Applejack reassured Twilight. "Everything's going to be ju--"
Suddenly, Rarity dashed to Twilight in despair.
"Twilight!" Rarity partially shrieked before reverting back to her normal tone. "Ugh. Sorry, darling. But I just realized you're not wearing your crown!" Rarity checked Twilight's entire head for any sign of said crown while she said that. "You haven't forgotten it back in Ponyville, haven't you?"
"It's in my bag." Twilight answered, which it then showed Twilight's bag next to Spike. "Just feel a little self-conscious about wearing it. Haven't really gotten accustomed to these yet, either." Twilight then unfolded her newly acquired wings from a few hours earlier. She then attempted to fly, but lost balance and dropped to the floor.
"You are a princess now, Twilight. Embrace it." Rarity encouraged Twilight. "I'm telling you, why if I had a crown like that, I would never take it off. Why, I'd sleep in the thing."
Twilight then gave a smile at Rarity, knowing her friend's love of elegant and regal attire. The group eventually arrived to the throne room of the palace, where both Princess Celestia, Princess Luna, Shining Armor and Princess Cadance were there to greet them as the royal guards blew their horns to Twilight's arrival. The Mane 6 were all taken by surprise by this as they entered the throne room. Deep down, Twilight felt that this was unnecessary. After all, she didn't wish to be treated as if she were like Celestia or Luna or even Cadance, she just wanted to be who she always was; herself. She failed to notice that she was about to bump into one of the guards, which happened soon afterwards. The guard was different than the other royal guards greeting Twilight. His coat was bright orange, his mane and tail were blue and he appeared to be wearing the standard gold armor that the guards of Canterlot wore, indicating he was also from the same place. The pegasus smiled seeing Twilight before him.
"Her highness! Princess Twilight Sparkle!" The guard exclaimed announcing Twilight's arrival.
"Twily." Shining Armor greeted his sister.
"Twilight!" Cadance then greeted her sister in-law. "I'm so glad I'll get to see you in your coronation tomorrow."
"We're all looking forward to your big day tomorrow, little sis." Shining Armor said to Twilight.
"We have so much to discuss, but it can wait until tomorrow." Celestia said. " It's been a long day for all of us. We better off to bed now."
Everyone then took Celestia's advice and went to their rooms to sleep for the coronation tomorrow morning. Twilight and Spike were getting ready for bed where Twilight was unpacking her things and Spike was fluffing his small bed. Twilight then pulled out her crown and decided to wear it to see what she looks like with it on in a nearby mirror. She sighed, which caught Spike's attention.
"What's wrong, Twilight?" Spike asked Twilight in concern.
"I don't know, Spike. I'm just worried, I guess." Twilight told Spike feeling unsure of her newfound destiny. "Princess Cadance was given the Crystal Empire to rule over. What if after I become a princess tomorrow, Celestia expects me to lead a kingdom of my own when I become one?"
"That would be awesome!" Spike said finding the idea...well, awesome.
"No, it would not!" Twilight disagreed. "Just because I have this crown and these wings, it doesn't mean I'll be a good leader." Twilight removed her crown and placed it on the bedside.
"Ah, sure you will, Twilight. Now, come on. You should get some shuteye. Big day tomorrow." Spike told Twilight as he tucked into bed, turned off the lamp and went over to his bed to sleep for the night.
Twilight appreciated Spike's support as she went to sleep. However, she was having some trouble doing so when her wings wouldn't fold.
"Can't...tuck..." Twilight said in frustration as her wings kept unfolding. "Just trying to get comfortable!" She seemed to have gotten them folded at last laying back down before the wings unfolded again, to her chagrin as she groaned in irritation.
During that night, as the guards were keeping watch over the halls of the Crystal Palace, one of the doors had a mysterious light coming from inside the room behind it through the keyhole. The door then opened before cutting to the perspective of the person inside the room watching one of the guards passing by and out of sight. A silhouette of a hooded figure was shown roaming through one of the halls, but stopped when the figure spotted the light from an approaching guard. The same guard walked in and the figure was hiding behind the wall to the guard's right and sneaked passed him while he wasn't looking. The figure then quietly roamed through the halls before coming across a room of interest as the shadows of legs appeared underneath the doorway and the door opened.
It revealed to be Twilight's room as Twilight and Spike were asleep. The hooded figure then entered Twilight's room, quietly approaching Twilight and carefully passing by Spike. The figure wore a grey hoodie, a backpack on her back, an orange skirt and black boots on her hind hooves. As the figure came up to Twilight's crown on the bedside, it appeared the figure was a orange-yellow unicorn with a red mane. The unicorn carefully lifted the crown with her telepathy, but ended up accidentally knocking over the bedside lamp. Fortunately for her, the unicorn managed to telekinetically catch the lamp just in time before it hit the ground, showing to be sweating on the forehead. The unicorn then looked at both Twilight and Spike and gave a quiet sigh of relief seeing they were still asleep. The unicorn then placed the lamp gently back onto the night stand and swapped the crown with a duplicate. The unicorn felt confident about having succeeded in taking Twilight's crown, decided to trot in victory for a bit before returning to the door. However, the figure failed to recognize Spike's tail on the floor and so the unicorn tripped over it as a result. The noise of the unicorn tripping then woke Spike from his sleep.
"Huh? What?" Spike said waking up.
The unicorn was trying to get back up on their feet, but Twilight was the second to wake and then notice her crown being placed into the unicorn's backpack, whom then sealed it.
"My crown! That pony's got my crown!" Twilight exclaimed pointing at the unicorn.
The unicorn now realized her situation and bolted out of there with Twilight giving chase.
"STOP! THIEF!" Twilight demanded, where the rest of the Mane 6 stepped out and were wondering what was going on. "That pony's stolen my crown!"
Hearing this, the other ponies soon joined in at helping stopping the thief.
Twilight tried to use her magic to unzip the unicorn's backpack. She managed to do so and reclaimed her crown with her magic. However, the unicorn noticed and used a teleporting spell on the crown to place it back into her backpack, though she didn't seem to zip it back up while Twilight went after her again.
The unicorn looked back and found the entire Mane 6 now chasing after her where Twilight caught up to the unicorn to reach for the backpack.
Twilight then tackled the unicorn into the room the latter came from where the crown flew out of the backpack and bounced around the room before fazing through the mirror, which the unicorn appeared to be glad about. The unicorn was then revealed to be a female and her mane was actually a mixture of red and yellow, almost resembling fire.
"What did you do with my crown?" Twilight demanded to the unicorn.
The unicorn's smile faded and gave Twilight a cold, scornful stare without saying a single word with a look as if she had a personal grudge against her. She soon teleported to the mirror and went through, to the Mane 6's gasp in shock.
"Who was that?" Fluttershy wondered.
Later that night, the Mane 6 had awoken and informed Princess Celestia, Princess Luna, Shining Armor and Princess Cadance. Celestia seemed to be the first to recognize the description of the thief that stole Twilight's crown.
"Sunset Shimmer. A former student of mine." Celestia said giving the Mane 6 the name of the intruder from last night. "She began her studies with me not long before Twilight. But when she did not get what she wanted as quickly as she liked, she turned cruel and dishonest. I tried to help her, but she eventually decided to abandon her studies and pursue her own path. One that has sadly lead her to steal your crown."
"She replaced Twilight's with this one." Spike informed Celestia taking out the fake crown that Sunset tried to replace. Celestia then analyzed the object.
"I suppose Sunset Shimmer thought you wouldn't notice right away that this was not yours." Celestia theorized as she walked past the Mane 6 to leave the room. "And by the time you did, it would be too late to go after your crown and Element of Harmony."
Twilight caught up with Celestia and asked her more about what was happening.
"But I don't understand. Where did she go? Where did she take the crown?" Twilight asked.
Behind them, everyone else followed them out of the room.
"You'll know more about this place than even I do." Celestia answered.
As they all left, it transitioned to the mirror from the previous chapter, which was now housed in a lone room in Cadance's palace, similar to how the mirror was back in Canterlot.
"This is no ordinary mirror. It is a gateway into another world." Luna explained to the Mane 6 standing to the left side of the mirror where her reflection was shown on the mirror. "A gateway that opens once every 30 moons."
Just as she finished, Pinkie raised her hoof from below Luna and touched the mirror, causing it to glow.
"Sparkly." Pinkie said entertained before Luna used her aura to remove Pinkie's hoof off the mirror and move her away from it.
"It has always been kept in our care at Canterlot Castle. But when Sunset Shimmer escaped into the mirror, Celestia entrusted it to Cadance for her to watch over." Princess Luna continued.
Celestia sighed in disappointment from behind the Mane 6 and stepped forward. "I had always hoped that Sunset Shimmer would use it to return, to come back to Equestria, seeking my guidance. Obviously, this is not what has happened."
"Twilight, you must use the mirror to go into this other world and retrieve your crown." Cadance informed Twilight, whom stepped up to the mirror while Shining Armor was by her side. "Without it, the other Elements of Harmony have no power and Equestria is left without one of it's most important means of defense."
Twilight nodded, understanding the situation and was ready to go into the mirror. The rest of the Mane 6 showed concern for their friend.
"Your crown does not belong in the place Sunset Shimmer calls home." Princess Luna informed Twilight. "And in her possession, your Element of Harmony will no doubt be used to bring harm to the inhabitants of this other realm. They will not have the power to defend themselves."
Luna then placed Twilight's saddlebag on her back, preparing her for her trip.
"You understand the importance of your task?" Celestia stepped up to Twilight and asked.
"Of course." Twilight assured to Celestia.
"Good. Then you must go at once." Celestia insisted.
With determination, Twilight sighed and made her way to the mirror.
However, Rainbow Dash then landed right in front of Twilight, stopping her.
"Whoa, whoa, whoa. If she's going, we're going with her. Right, girls?" Rainbow Dash insisted as the other members of the Mane 6 then joined her.
"Ooohh! I'm nervicited!" Pinkie Pie excitedly said.
"You do realize that's not a real word, right?" Applejack asked Pinkie.
Twilight was touched by her friends' loyalty and made a warm smile.
"If you truly wish to go, then I won't stop you." Celestia assured, to the Mane 6's delight. "But you all must go at once."
"Time is of the essence. On the third day, when the moon reaches its peak in the night sky, the gateway will close." Luna then explained. "And once it does, it'll be another 30 moons before you will be able to use it to return."
With nothing else stopping them, Twilight stepped up to the mirror first where she raised her hoof to touch the mirror. The hoof then went through the mirror a bit and took it out in hesitation. She looked back at Celestia, who nodded her approval and so Twilight stepped into the mirror first.
As Twilight was about to enter through the mirror, Spike then saw what seemed like a sinister figure reflected on the mirror's surface and it looked as though it were about to attack Twilight. Spike then dashed to Twilight's aid, but tripped as he then knocked both her and himself into the mirror. The two were then changed into small light spheres traveling through a rainbow colored tunnel, almost reminiscent to the Bifrost from the Thor films. As the spheres reached the end, a bright white light flashed covering the whole screen.