Luna had finally finished college and had moved on. She still lived with her sister and had become a guard too. Only, she was a guard of the night, which meant that she guarded throughout the night. One night, during Luna's shift, three small Chaos creatures came and attacked Ponyville. All the guards defended the houses bravely but they were losing. Guard after guard fell and the day-shift guards were called in. This included Tia. Tia and Luna fought side by side to defend the village, they were the strongest out of all the guards. Soon, they were the only guards left and very few citizens remained alive, most had been crushed when the houses had collapsed, the lucky few who'd survived, remained silent. Luna and Tia were tired. They stared on at the remaining Chaos. Chaos were not particularly hard to kill, but they were very good at dodging and they were quite fast, so you had to be quick. The remaining chaos looked like a tiger, with bat wings and dragon claws. It shot beams of fire and Chaos magic at the two sisters constantly, Luna managed to hit it in the chest and the chaos beast stumbled. Tia took the opportunity to fire a beam of magic at it, but the Chaos managed to dodge it in the last second, and it charged up a very large ball of chaos energy. Tia and Luna braced for Impact, they started to charge their horns. As the Chaos let the energy ball fly towards them, Tia and Luna, synchronized, produced a magical barrier, the energy ball hit the barrier and the barrier exploded, but the energy ball kept going. At that time both sisters panicked, they both knew in that instant that everypony in Ponyville would die and they would fail as the guards they were, but, then, something happened, they both felt a magical surge, being channeled by their will to save everypony. Tia and Luna became overwhelmed by the amount of magic flowing through them. Together, they had a magical outburst. Luna projected the power of the moon down on the Chaos, and Tia, bringing up the sun, projected its power down on the Chaos as well. A solar eclipse was formed and the power of the sun and the moon combined shone down on the Chaos. The Chaos then exploded into smithereens, the eclipse also created a huge magical aura that surrounded Equestria, destroying all the Chaos everywhere. Luna's and Tia's magical outbursts stopped, leaving them both with a cutie-mark each. They looked at each other in delight, nopony had teased them about being blank flanks, but that was because most ponies never got a cutie-mark, it was a rarity. Tia's cutie-mark was a sun, and Luna's was a moon.
They were so happy about getting their cutie-marks that they didn't notice everything else that had happened. They had wings, the Chaos had been defeated and in it's wake, lay 6 colourful jewels sitting on a gorgeous ornament table. As the surviving ponies came out from what was left of their homes, Luna, moved the moon so that it was daytime. The surviving ponies looked around, some ventured forth towards the jewels, others stared up and the two alicorns, one of which was lowering the moon with her magic. A whisper began to flow through the crowd and soon everypony was staring at Luna and Tia. The two alicorns turned round to find everypony staring at them. One pony bowed and soon, everypony else followed him. Luna and Tia looked at each other in confusion, then they saw their wings. Their jaws dropped. Alicorns were supposed to be the rulers of Equestria, though none had been seen since the war against the Chaos had started, which was over 7 thousand years ago.
A zebra stepped forward from the crowd, she hadn't been there before, Tia knew this,
"Welcome, Princesses. Kindly tell us your names." Tia, thought that the zebra was suspicious, after all, she had more or less appeared from no-where, but she stepped forth none-the less,
"My name is Celestia and this is my sister, Luna" Luna stepped forward at the mentioning of her name. "We have defeated the Chaos and may Harmony forever flow across this land." Celestia said, taking the role as the leader since she was the older sister.
"Welcome, Princess Celestia and Princess Luna, you shall forever keep the peace and protect us from evil?" The zebra questioned. Luna though this was a silly question, but her sister answered as if it were normal.
"Yes, we shall, and we will also keep the day and the night in an everlasting routine, I shall bring you the day and Luna shall bring you the night."
"Might I suggest you also once again create this eclipse, every so many years to celebrate the Chaos's defeat?" The Zebra asked.
"Yes, we shall, every decade, on the longest night of the tenth year, we shall bring you this eclipse to banish the chaos and bring joy to you all." Celestia was full of herself at that moment, defeating Chaos and becoming a ruler of Equestria in one day, she was being overwhelmed with the sense of power, but she managed to hide it.
"Wonderful, now where would you like your castle to be built?"
"What castle?" Luna questioned, having just found out that she's an alicorn and has defeated (with her sister) an army of Chaos creatures that would double in numbers every year and could kill as easily as dodging a dodge ball, caused Luna to miss the fact that Princesses live in castles.
"Why, the castle that you are going to live in of course!" the zebra replied with a chuckle.
Celestia had a small grin planted on her face, her sister could be pretty funny at times, "Well, How about we put it in the everfree forest, that is where the Chaos started, so by putting it there we could easily protect you from any more dangers."
"Wonderful, then follow me to where it shall be built and we will get started on the preparation"
"Wait," Celestia called, "what is your name?" she asked, pointing at the zebra.
"My name is Arocez" She replied.
Somepony from the crowd called out
"What are we going to do about these jewels?" Celestia, Luna and Arocez looked at the jewels the pony was pointing at. Each one had a magical aura coming from it.
"We'll leave it there for now, as soon as the castle is built, we shall move it into there." Celestia decided.
--------------8 months later-----------------
Arocez lead the two alicorns to the castle. It was gorgeous, tapestries with both Luna's and Celestia's cutie marks on them hung down from the wall just above two large and comfortable thrones. They discovered a lot of secret passages and tunnels, Arocez had put them there, so the two young alicorns could have some fun. They lived in the castle for thousands of years, protecting Equestria from evil. They eventually found out what the jewels did, they destroyed evil and brought harmony, so they called them 'The elements of Harmony'. They decided never to use them, only when it was absolutely necessary, the Elements became Equestria's last line of defence, they were never used, until one fateful day...
Celestia loved her reign as Princess, however, as her reign went on over thousands of years, Luna became jealous, she wanted to be the main ruler of Equestria, make the big decisions, be the princess everypony knew, even if it was just for a day, but Celestia wouldn't allow it. To Luna, it seemed that Celestia grew more and more self obsessed, she only cared for herself. Celestia denied this, she kept telling Luna that she did care for her citizens, but Luna saw past this, Luna knew that Celestia made it seem like she cared, when really, she didn't. Luna thought she could be a better princess than Celestia, that Celestia didn't deserve to be the ruler of Equestria, that there could only be one princess.
Luna challenged her sister to the throne, it was the longest day of the tenth year, when the solar eclipse was supposed to happen, instead, Luna brought up the moon in front of the sun and formed a Luna eclipse, the Chaos power in that eclipse surrounded Luna, transforming her into Nightmare moon! Another magical outburst occurred, this time, channeled by hate. All the hatred she had for her sister, all the envy for her sister because she was the ruler, all of this that she had kept bottled up, came out as her fourth magical outburst in her life. Nightmare moon refused to lower the moon and told Celestia what she thought.
"There can only be one princess in Equestria! And that Princess, SHALL BE ME!!"
A great battle took place then, magical beams shot from the castle as both princesses fought for the throne, the walls crumbled as they were hit, the battle was taken into the air, both princesses diving at each other and shooting lasers from their horns. Nightmare moon managed to knock Celestia down into the castle, she laughed at how close she was to victory, she then dived down towards where Celestia was falling.
Celestia had fallen right next to the elements of Harmony, she looked at them, then back at her sister, and knew the time had come to use them. Regretfully, she levitated them with her magic and set them off just as her sister was about to hit her. The blast sent Nightmare moon flying towards to moon and it banished her there, for 1000 years.