Prologue
The Night Thief

It was a calm and peaceful night in Ponyville. Not a single pony was awake. The streets were empty and barren, except for one hooded figure that was darting from house to house, trying hard not to be seen. It wasn't before long he finally made it to his destination, Golden Oak Library. He cautiously opened the door and went inside. He then slowly walked across the room and approached the case where the Elements of Harmony were kept safely inside. The pony noticed the case was held tight by a steel lock, but that didn't faze him one bit. The pony then reached up and pulled back his hood reveling a horn. This pony was actually a unicorn. The unicorn activated his magic and quietly broke the lock handle. After he put the broken lock on the floor, the unicorn reached into his cloak and pulled out a brown sack. He then put the Elements of Harmony into his sack one by one. After the case was completely cleaned out, the unicorn put the sack containing the Elements of Harmony onto his back and went back outside. Now that the first part of his mission was finished, the unicorn began to ran as fast as he could and left the town of Ponyville. After nearly three hours of nonstop running, the hooded unicorn finally arrived at Canterlot. However, he noticed that the entrance into the capital was guarded by two royal guards. After the unicorn made a noise to make one of the guards come near the bush he was hiding in, the unicorn managed to knock out the royal guard. After the other royal guard decided to check on his comrade, the unicorn was able to knock him out too. Now that the entrance to Canterlot was unguarded, the unicorn quickly entered the city and made his way quietly through the streets. Eventually, the hooded unicorn was able to successfully make it all the way to the castle. However, this was where the true challenge began as the castle was filled with guards roaming around everywhere. If he accidentally bumped into one, there was no way he would be able to escape without being caught. Luckily for him, the unicorn managed to avoid running into any guards. A few minutes later, he made it to a room. He quietly opened the door and went inside. What was standing before him was none other than a tall elegant mirror. "So...this is where that old hag was keeping it," the unicorn muttered mischievously. He then grabbed his cloak and tossed it to the side of the room. This unicorn had a white coat with a black mane and tail. His cutie mark was a set of pipes with blue flames blowing out of them. He slowly approached the mirror and moved right his hoof towards it. Amazingly, his hoof went into the mirror, like it was made out of water. He quickly pulled it back out and smiled. The unicorn then took off his sack and opened it. He reached in and pulled out a piece of paper that had writing on it. Just looking at what was written made him chuckle. He then tossed it carelessly behind him. After he put the sack on his back, the unicorn jumped into the mirror head-first and disappeared. The next day, at Golden Oak Library, Flareon woke up to another morning. After he fed Chibiterasu and Owlowiscious, Flareon went downstairs. What he saw completely froze him in fear. The Elements of Harmony were gone.

"Twilight?! Twilight!" Flareon yelled in a panic state, "Come down here!"

"What's wrong Flareon?" Twilight muttered as she rubbed her eye trying to wake up.

"Look!" Flareon yelled at the empty case, "The Elements of Harmony are gone!" Immediately, Twilight began to realize the danger of the current situation at hand.

"Oh no!" Twilight exclaimed, "Who could've done this?" It wasn't long before Spike came running downstairs with a letter in his claws and they immediately began to read it. The letter was from Princess Celestia telling Flareon and Twilight to come to Canterlot ASAP.

"Spike...tell Solana when she wakes up that we went to Canterlot," Twilight said as she put the letter on the coffee table, "We'll be back later." She then turned to Flareon. "Let's go."

"Are you sure you're ready to fly all the way to Canterlot?" Flareon asked concerned, "You only started to learn how to fly a couple of days ago. The long flight could cause your wings to hurt."

"Don't worry," Twilight replied as she put her right hoof softly on his shoulder while giving him a reassuring smile, "I'm ready. After all...I do have a great husband for a teacher you know." Soon after, Flareon and Twilight waved goodbye to Spike and went outside. They quickly flew into the air and made haste for Canterlot to speak with Princess Celestia. Thirty minutes later, they finally made it to Canterlot and flew over to the castle. As they were walking through the hall to the room where Celestia was, the royal guards stood firm when Flareon and Twilight walked past them.

"Hail Prince Flareon and Princess Twilight!" they shouted proudly. In response, Flareon smiled and couldn't help but laugh a little.

"I still haven't gotten used to that yet," he said. Shortly after, they went inside a room where some royal guards were talking to Princess Celestia. Near them was a beautiful mirror. When Celestia spotted Flareon and Twilight, she immediately dismissed the guards and went over to them.

"Thank goodness you two are here," Celestia said. They could tell that she was very stressed and tired.

"Princess Celestia...someone stole the Elements of Harmony!" Twilight exclaimed. For some reason, Princess Celestia didn't seem surprised at all.

"Yes...I know," Celestia replied, "I got reports from some of my guards that someone infiltrated Canterlot. It seemed that the culprit knocked out two royal guards near the city entrance. Luckily, they were left unharmed, just knocked unconscious. From what I know, the culprit's trail ends in his room. They must have gone into that magical mirror."

"Wait...magical mirror?" Twilight asked puzzled, "When did you get a magical mirror?"

"I bought it at a flea market in Fillydelphia last week," Celestia replied somewhat proudly, "I got it at a pretty good deal. It only cost about 15 gold coins. Apparently, this mirror is actually a portal that leads to another world."

"What world?" Flareon asked, "Hold on...you're telling me you bought a mirror that leads to another world at a flea market? For just 15 gold coins? Seriously...you've got to be kidding me. Does anyone else find this impossible to believe?"

"Um...I actually have no idea what world this mirror leads to," Celestia replied embarrassed, "The guy who sold it to me simply said it lead to another world. That's it." Sadly for Flareon, his other question was never answered. Just then Princess Luna came into the room. "Sister...have you learned anything from that note?"

"I'm sorry, but none of this make sense to me," Luna replied. She then turned to Flareon and Twilight. "Maybe one of you can figure out who stole the Elements of Harmony from this message the culprit left behind." Once Luna gave them the note, Twilight used her magic to hold it before her and Flareon.

"I have stole your precious Elements of Harmony and gone into the mirror," Flareon read. He then looked at the bottom where another message was. "Catch me if you can Angel." After he was done reading the note, Flareon noticed that Twilight was fidgeting nervously as if something was bothering her.

"Twilight...do you know who wrote this?" Flareon asked. In response, Twilight let out a deep sigh.

"His name is Nitro and he's a unicorn," Twilight replied, "Also...Nitro's my ex-boyfriend. He used to call me his Guardian Angel."

"Wait...what?! Ex-boyfriend?!" Flareon exclaimed shell-shocked, "Why was I never informed about this guy Nitro? When was the last time you two met? Are you still seeing him?" Twilight pretended not to hear him. He then turned to Princess Celestia, who also seemed as if she knew who Nitro was. "Who the heck is this Nitro guy anyway?"

"Nitro used to be part of my royal guard," Celestia stated, "He was the vice-captain ranked under Shining Armor at the time. Nitro suddenly resigned shortly after you and Twilight were married. I never heard from or saw him ever again after he quit."

"Me and Nitro were very close. I loved him and he loved me, but...Nitro had this dark side that I came to fear and that's why we broke up," Twilight said as the memories of Nitro were painfully starting to return, "It all began back when I was in Princess Celestia's School for Gifted Unicorns twenty years ago." Twilight started to tell everyone about the unicorn named Nitro and her past relationship with him.