The History of the Crystal Empire
Long ago, in the earliest years of Equestria, there stood a beautiful and valiant empire. The Crystal Empire. The empire was peacefully ruled by Queen Chrysalis and King Sombra. The changelings and crystal ponies lived in harmony and prosperity as well. As the ponies would fuel and charge the crystal heart with love, the changelings would use that love to gain an extra kick in their step to continue on with daily doings. It was a lovely era of peace and benefit.
One day, whether born or taken in, a young pegasus filly entered the royal family. Her name was Cadenza Mi Amore. Later, she earned the nickname of Cadence. She was a very friendly little filly, spreading joy wherever she would wonder. All the residents of the Crystal Empire were delighted by her presence. And though she could not technically perform magic, being a pegasus, the crystal ponies could swear that the magic of love radiated from her and filled everyone with bliss and amity.
But, as fate says, all good things must come to an end. When Cadence was only just in her late filly years, disaster struck. King Sombra became corrupted, perhaps by means of the Alicorn Amulet. None the less, the empire was thrust into darkness. Queen Chrysalis was hesitant on trying to combat Sombra, someone so dear and close to her. Instead, she began to evacuate the empire. Chrysalis sent Cadence out of the empire, told her to fly away as far as she could and to get somewhere safe. Unwillingly, she fled into the forest nearby and out of the collapsing empire. Next, the changelings could easily escaped with their wings, but the crystal ponies, being mostly earth ponies, weren't as lucky. They were enslaved by Sombra and the love and light that had once resided in their hearts, diminished.
Queen Chrysalis finally fled the empire with her subjects, stricken with sorrow and pain. She did the only thing she could think of, and sought help. She came desperately to the royals, Princess Celestia and Luna. The sisters, harnessing the power of the Elements of Harmony, overthrew Sombra and he was turned to shadow. But, when the news returned to Queen Chrysalis that her nation, her spouse, half of her subjects, and her home had vanished into thin air, she shifted the blame onto the royal sisters and blamed them.
(And at one point, Celestia and/or Luna find Cadence in the small nearby earth pony village. They saw how she spread love and light even though she lacked unicorn magic. They took in the pink pegasus, who was now in her teenage years, and granted Cadence her alicorn and princesshood along with being accepted in as Celestia’s niece.)
Chrysalis and her changelings, now having very little supply of energy, were desperate. Her entire army went on a feeding spree, demolishing large sections of Equestria and draining the love. The energy in the changelings and Chrysalis skyrocketed. But the spree did not last long before the Princesses caught wind of the news. They then, rose up against Chrysalis and banished her to the depths of Tartarus. But not before her Changeling army fled, but their forms diminished for their energy had plummeted from the high point they were at.
After years upon years of rotting away in Tartarus, Queen Chrysalis finally saw her chance to escape when the three-headed dog, Cerberus, had left his post. Not too long later, she returned, stronger and wiser than before and sought power. She launched a skilled attack onto Canterlot, first by slipping in and posing as Princess Cadence.
(and you basically know how that turned out)
Queen Chrysalis was ultimately defeated again and cast away. Perhaps planning another attack but waiting for the perfect time… to strike again.
