Long, long ago before time Equestria was nothing but a collection of fields and pastures. The various races of ponies and creatures were spread out across the land. Not really having any reason to co-operate or unite, they remained in small groups across the land and rarely interacted outside of trade and conflicts. That was until Grogar had came along. Grogar was the 'father' of monsters and had ruled with an iron hoof as he declared himself 'emperor of all he saw'.
Seeing this, the 3 races of ponies organized themselves into armies. Forced to fight off the monsters, and Grogar's legions they were forced to come together as 3 races. Without Grogar's powerful influence and threat over the land, there would have been no reason for the 3 tribes to form armies to rise up against his rule. The 3 tribes formed civilization, and organized themselves. They built cities, towns, and armories to fight off the forces of Grogar. Although not constant warring, Grogar's presence loomed over the land constantly.
Gusty the Great had lead a Unicorn army to reach the city of Cloudsdale, the capital of the Pegasi. She was there to reach out to the Pegasi for an alliance against Grogar. However Grogar had forseen this through his crystal ball. He and his army of monsters had set out to confront the army of the Unicorns. A fierce battle ensued. The Pegasi had seen this from the city of Cloudsdale and looked on as the battle happened. Their leaders had decided to help the Unicorns out, and the Pegasi flew down and engaged in combat with Grogar's army. Grogar's army was incredibly powerful, yet the Pegasi and Unicorns were determined. As Grogar began losing some of his army to causalities in the battle, Gusty the Great had noticed the bell around Grogar's neck, the source of his power.
It was then she realized the way to defeat Grogar. The battle ensued for what felt like an eternity, and Grogar was left alone after some of his monsters fled, and the others perished from the battle. Then Gusty cried out for everyone to strike Grogar at once, and as Grogar was distracted she stole the bell out from under his chin. Grogar was weakened, and thus his tyranny had ended. She cast a spell to keep it in place, guarded by the winds atop Mount Everhoof.
To deal with Grogar, Gusty the Great had banished him into the stars - creating the constellation Ares in the Night Sky.
After Grogar was defeated, the 3 tribes had a tense but stable peace for years. When the blizzard had came, their representatives had met. The Unicorn representative of Princess Platinum, Puddinghead of the Earth ponies, and Hurricane of the Pegasi had met. King Cobalt, was the King of the Unicorns. He lusted for power and he had all the power he had wanted, and was very angry that he had to share it with the other leaders as the tribes were now one nation.
The 6 unicorn wizards tasked with bringing forth day and night, were growing more weary and old with each cycle. This caused great distress in the young Equestrian nation. 2 unicorns stepped forward to take the wizards place. They were Celestia and Luna. When Celestia and Luna would raise and set the sun/moon for the first time, the cold, weary ponies would be incredibly regretful, while King Cobalt watched them with scorn and hatred. They shared their love. The 3 tribes's magic flowed into them through love, and they became alicorns. King Cobalt could only watch in jealousy and envy.
When the 2 alicorns came to be, King Cobalt was forced to step aside from the throne as all 3 tribes had the new alicorn leaders - they didn't need a unicorn King any more. With bitter hatred, the King conceded and stepped down, though taking note of what happened. From that time on, he had studied ancient and forbidden magic...biding his time.
As the King studied, there came another pair of sisters. Cavatina, and Bravura. They were sent by Celestia and Luna to explore new lands and took some others with them. After a long time of exploring, it was decided 2 sister cities would be built in honor of both of them after the 2 of them saved the crystal ponies, another race of ponies to the North from various attacks from monsters and other ponies. The crystal ponies were greatful and they split into 2 different groups, one for each new city that would be built in the 2 sister's honor. This created a rift between the 2 of them. The 2 cities would compete in building, who could build faster, and better? Bravura's city was the first built, while Cavatina's was finished a day later.
Bravura was adventurous, daring, and brave, while Cavatina was modest, and compassionate. They would clash / argue sometimes, but at one point their relationship would break. Cavatina had followed the legend of the crystal heart. A legendary crystal that would give immense power to those who used it, and protect the city's inhabitants from the cold wind using it's magic. After locating the crystal, she had proudly displayed it in the center of her city. Bravura, seeing this from a distance scowled in hatred upon seeing her sister's city enveloped by the protectful spell dome, while her city wallowed in the cold. Her heart internally would break upon this. She believed her sister was being selfish...yet she was the one who wanted to steal the heart for herself.
During the Summer Sun celebration, the ponies back in Equestria were met with their old king. Looking more sinister and dark then ever, he crafted a dark spell and took the magic of the audience for himself - crafting himself into a fearsome, dark alicorn. From that point on, he would be known as King Sombra. Using dark magic, he fought with the sisters and overthrew them.
He ruled with an iron fist, demanding the allegiance of all those beneath him. As this happened, the 2 crystal cities had grown more and more violent towards one another. Specifically, it was Bravura who would instigate the conflicts. She wanted that crystal heart for herself, and the crystal ponies under her rule grew jealous and hateful of the neighboring city who refused to share the hearts light with them - as it could only protect so much and so many.
Bravura had hired the most talented and daring ponies to go and steal the heart. She had them disguised as rogue thieves or among rogue tribes that would ransack the cities if they didn't defend them. She sent them to steal the heart. They had failed in their task and were either arrested or came back with failure. Bravura scolded them harshly, and would go to take the heart for herself. That night, she would have snuck into her sister's city and took the heart for herself! But Cavatina saw this, and they got into a really heated argument over the heart. Cavatina tried to reason with Bravura, she wanted to find a way to create or find another heart so Bravura could use it, but Bravura saw this as lies and deceit.
She would rip the heart from Cavatina's grasp, and with an incredible lust for this power began to steal it's energy. It's energy began to swarm around her, in a bright glow it'd crash down onto her. Then, after the light cleared, Bravura would be standing over Cavatina...as an alicorn and with darker colors. She imprisoned her sister in the dungeons and took possession over the dual cities for herself. With the heart's power surging through her, and the admiration from the crystal ponies she would be satisfied for once, while her sister wallowed and weeped in the dungeons.
Bravura's inhabitants were given extra privilege and rights, while Cavatina's population were seen as second class citizens and pushed around. Bravura was overjoyed with this power, and looked on to Equestria as King Sombra had waged war on the other races and ponies of the land. Seeing an oppurtunity to conquer Equestria, Bravura had sent Catavina's population to fight in the battles, forcing them to fight while her own population sat behind, and dined in luxury as Catavina's population fought the fierce battles with Sombra's mind controlled army. Bravura had intended to become the first Empress of Equestria, a title she held for a very short time as Bravura's forces knocked Sombra's out beyond Equestria. But it wouldn't be long before a massive counter-attack occurred, allowing Sombra's forces to return home.
Bravura and Sombra had engaged in a direct duel, neither of them could break the other's will. That was until, they heard a call from the side. Starswirl the bearded, Celestia, and Luna had stepped forward from the shadows. Bravura looked to them, and seeing her 2 friends once again, they all joined forces against King Sombra, and defeated him. Starswirl took a gem, and took the magic he stole and put it into the gem - as it would be too far corrupted to return. He crafted a frame of Sombra's image on it, and banished King Sombra to beyond Equestria.
Bravura had gleefully thanked the others for helping her in the battle, however Luna and Celestia had noticed that Bravura had changed. She seemed different than before, and her sister wasn't there. They inquired of it, Bravura snapped at them and then fleed home with the weary crystal army. Luna and Celestia looked concerned at the state of the army, and one of the ponies had told them of Bravura's cruel rule and betrayal of her own sister for power.
Celestia and Luna had journeyed to the crystal Empire, along with Starswirl. The crystal pony who's name was Radiant Hope told Celestia and Luna where Cavatina was held. They freed her, and Cavatina along with the others had confronted Bravura. Cavatina gave a speech as Bravura looked over them all from her high throne with scorn, she gave her population motivation and with that, all of the ponies bowed before Cavatina, aswell as Celestia and Luna who lended their own magic to help.
A massive white light would soar towards the throne, knocking it off and carrying it to Bravura's city in which the throne crashed, knocking Bravura out and leaving her population confused. Celestia, Luna and Starswirl would use the power of all the 'free' ponies and those who resisted Bravura's rule. In a great spell cast, and this happened to coincide with the planet Wistrol's opposition date (when the planet is closest and highest in the sky / closest in the planets orbits), a wave of magical energy would be sent at Bravura and her warring army...whooshing them away to he planet, never to be seen again.
Sombra could only watch from a distance as this was going on, stunned.
Bravura and her city were banished / transported to the planet Wistrol. A large planet, about twice the size of the planet Equestria. It was cold - not unlike the northern regions of which Bravura's city resided. They were stranded on another planet. It was hard to breathe. The air was a bit thin. The sky was covered in a purple haze that prevented them from seeing the majority sky in most cases. Her city would lay wrecked across the wasteland landscape of the planet Wistrol, an uninhabited, frozen desert world. The ground was of a yellow-tan color, not unlike Bravura's mane. When Bravura had woken up, she would be shocked and weakend from the spell. All of the ponies had been affected by the higher gravity, which was around 10% more on this planet.
Bravura's crystal ponies had worked on finding food, finding strange purple plants that would grow squelchy bulbs of various colors. These plants allowed them to stay fed, however over time they fused a magical property in these ponies that allowed them to be more resilient and able to withstand the harsh enviroment. They nursed Bravura back to health with these plants...and the city would begin rebuilding...
Back on Equestria, King Sombra leered at the crystal heart from a far one night. He would strike when the guard would be low. And this time, he would rule the Crystal Empire with an iron hoof. After a while the 2 sisters would banish him under the ice, after he failed to fend off the last attack on his reign.
By the time of Twilight Sparkle's time, Bravura's crystal city had grown into a massive nation that had lied in the Equatorial areas of the planet Wistrol. A lot of the planet was host to pony population, colonized over the course of the next 1,000 years. Small towns, cities had been built. Bravura's reign never falted again, as there were no enemies to face. Bravura had ruled her subjects fairly yet harshly in order to survive. With no enemies here, the city was able to prosper but hidden beneath the haze and so was never seen from Equestrian telescopes. Bravura had her ponies construct a huge telescope upon a nearby mountain that stuck out of the clouds. She would always keep a watchful eye over Equestria and it's events.
By then, the crystal ponies had completely adapted after generations. They were able to breathe the air naturally, their heart and lungs evolved to suit that. Their eyes and pupil changed a little bit to take in the darker light with more effectiveness, and had thicker coats to deal with the cold. They were also slightly shorter and stronger because of the higher gravity. They would be perfect warriors on Equestria, but they couldn't breathe Equestria's air for long as it would be too warm, wet, and thick for them.
And as since Equestria has never built any form of rocketry, Bravura's reign over Wistrol would forever be uncontested as they continued to expand their influence over the planet...
Her reign would truly last forever.
Centuries later, Grogar would use his magic to manipulate 4 stars into setting Nightmare Moon free from her imprisonment.
( Credit to @LyraLover 💚 for the planet Wistrol, and the names of Bravura and Cavatina. And also credit to @Lunarpalette for drawing Bravura in 2017.)