The doors of Twilight's Castle opened, and in walked a grey colored stallion wearing a gray/blue delivery man's uniform, pulling a wagon stock pilled with books from the Canterlot Library.

"Excuse me, Princess. Where do you want all these books from Princess Celestia?"

"The library." Twilight said.

She then pointed towards the direction of the library. "Third door on the left."

"Even this one that's glowin' and vibratin'?"

Everyone's eyes shifted to a book that stood at the very top of the pile, which was indeed glowing bright and vibrating. Twilight levitated the book downwards, which had an image of Celestia's cutie mark on the cover, and began flipping through the pages. She landed on the final page, which was the only last one that had words written on it. Her eyes widened in surprise.

"What is it, Twilight?" Fluttershy asked.

"It looks like a message to Princess Celestia from my friends at Canterlot High."

Twilight read the message. "From Sunset Shimmer to be exact."

"I have no idea, but it... sounds like they need help."

"The way Sunset Shimmer described them, I think these new girls sound an awful lot like... the sirens."

"Not the sirens!" Pinkie Pie exclaimed in terror. She then stretched out in closer to Applejack, whispering loudly, "I don't actually know what that is!"

Twilight began narrating, "Many years ago, when Equestria was still very young, there lived these three magical creatures known as the sirens, who roamed the sees charming ponies with their music."

Rarity leaned forward to look at the picture of the sirens. They were these horse-like beings with fins on their hooves and near their ears, as well as long elegant transparent large fins across their spines that gave the impression of hair, as well as long beautiful fish-like tails and red pendents on their chests.

"They're beautiful."

"Yeah, they are. But also incredibly dangerous." she flipped the page, landing on another image of the sirens, who now looked far more sinister than in their previous page as Twilight continued the narration.

"While their music was indeed very powerful, in order to maintain it, they had to feed on the negativity and distrust of others. The more of this negative energy they consumed, the stronger their voices became, and the farther they could spread their dark magic."

Fluttershy began to shake in fear, "I don't think I like this story very much."

Twilight continued her narration. "In fact, they took advantage of the disharmony among the three divided pony tribes during the blizzard of the windigos. But once they were driven off, they needed a new source of energy. They came across the portal, not too long after the rerbel ponies did, and traveled into the human world. For years, they wandered the continent, taking advantage of the negative emotions from the all creatures until elite team of five mystical creatures uses their own music to fight the sirens. With their hypnotic voices, the sirens caused a rift between humans and ponies, and the two species were soon drawn into an all out war."

The room grew silent for a second before Twilight continued, as the others listened attentively, both concerned and rather frightened by this ancient tale.

"But The Mystic Beats weren't having the sirens get away with it. Together, they used their combined magic and music to defeat the sirens, rendering them powerless. They requested the help of a very talented unicorn wizard, Starswirl the Bearded, to find a way to imprison the sirens. He created a magic mirror and banished them into another land, distant from ours. As for the Mystic Beats they used all their powers to seal the sirens and themselves in order to prevent any threat from Equestria from crossing over to the human world again."

Once the tale came to a close, Spike spoke, "So, that world Starswirl banished them to must be where Canterlot High is."

"But if Star Swirl sent them there ages ago how come they're just surfacin' now?" Applejack asked.

"I don't know." said Twilight, "But if my hunch is right and it is the sirens who have come to Canterlot High, this spell they've cast is just the beginning. And with the Mystic Beats out there somewhere protecting the human world."

"My friends need me. I have to get back to them." Twilight attempted to leave towards the mirror portal, which was moved from the Crystal Empire to Twilight's castle. But Rainbow Dash flew ahead and landed in front of her

"I hate to burst your bubble, Twilight, but the connection between their world and Equestria will still be totally cut off for a super long time."

Pinkie Pie appeared in between them unexpectedly. "Okay, first of all, if there was bubble-blowing going on, why wasn't I told about it?! And secondly, if the connection is totally cut off, how was Sunset Shimmer able to get a message to Twilight?"

Twilight thought about this for a second before gasping in realization with a wide smile. "Pinkie, you're a genius!"

Pinkie Pie smiled proudly as Twilight galloped away excitedly. "Yeah, I get that a lot." she turned to Rainbow Dash, grabbing her by the neck, and her eyes nearly bulging out of her head. "Now about those bubbles…"

The alicorn princess returned a few seconds latter, happily levitating some gadgets and gizmos, long electric cords, and various other scientific gadgets and began to place them all together around the portal mirror. The others watched in anticipation and curiosity at what the alicorn was doing. Once she was done, the mirror was surrounded by wires, and other electronic items hardwired into the mirror. It was like Twilight had created her own science lab in only a short amount of time.

The princess stood back proudly at her work. "…And the interval between the two points is defined as the square root of the sum of the squares of the separation between the points along three spatial dimensions."

However, sometimes Twilight forgot that not all of her friends understand her science speak. They all looked at her with either confused or skeptical looks. Spike was the first to say, "Say what now?"

Pinkie Pie rolled her eyes, "Duh! She's gonna take the magic in here" she pointed towards the book where Sunset sent the message, "and put it in there." she gestured to the mirror, "That'll make the portal open up so that whenever she wants to, she can go from here to there." she pointed to the book before doing a cartwheel in front of the mirror, and continued going back and forth from both objects, "There to here. Here to there. Here there! Here there! Here—"

"We get the idea!"

Pinkie stopped, still smiling.

"Now to see if it actually works." Twilight said as she levitated the book and placed it on the very top of the generator and the sun symbol began to glow bright, sending magenta colored electric charges to the metal antennas which coursed all the way down, through the cords and everywhere before reaching at the very top of the mirror, which then began to glow brightly and a magenta colored swirling vortex appeared within the glass. The portal was now up and running.

Everyone all gasped in awe at the accomplishment.

"Don't suppose we co uld join you this time around?" Applejack asked.

"Better not." said Twilight, "It could make things pretty confusing if Canterlot High all of a sudden had two of all of you."

The Ponies all looked at one another before nodding in agreement.

"But I still get to go, right?" Spike asked, "There isn't another one of me at Canterlot High. And you never know if you might need your trusty assistant."

Twilight nodded in agreement, "Mm-hmm."

Spike jumped up with glee, "Yes!"

"Ready, Spike?"

Spike cracked his knuckles, blew and squeaked his claws. "Ready!"

With fierce determination, the two ran into the portal, which glowed brightly once they entered. The others remained watching the portal with worried expressions.