Prologue: Children of The Crystals
A long, long time ago, before King Sombra's frightening arrival in the Crystal Empire, there was a small town called Crystaltown. Crystaltown is what the Crystal Empire used to be before it grew huge. Crystaltown was what many of a rare pony breed called crystal ponies called home. The town's population at this point in time was only fifty four.
Today happened to be one of those days when a chilly blizzard was blowing. It was so windy that it blew out candles from the inside of some homes. The mayor of the town, Ruby Lake, advised the very few ponies living in Crystaltown to shut the doors and windows. This blizzard was the worse blizzard on record.
Later, in the night, the blizzard finally came to a jarring halt. Snow covered nearly all of the homes in Crystaltown. However, the wind was still blowing almost as hard as it was during the chilly blizzard. By this time, everypony was asleep...
Except for Ruby Lake. She was light red and had the cutie mark of a glistening dark red ruby. Her eyes were a burning green and she had a cerise mane. She was simply just picked to be mayor of Crystaltown because of her great leadership skills. Being mayor sure was tough.
She was checking outside of Crystaltown to make sure that nopony got frozen or covered by snow. That would be horrible because she would be shamed by a rare species that she was a part of. Her life would suck then, and she would have nowhere to turn to and no place to live.
"Anypony out there?"
The other fifty three citizens of Crystaltown were, luckily, safe and sound inside their homes. However, since everypony else was asleep, Ruby Lake decided to go exploring into the outskirts of Crystaltown.
Nopony knew what lay outside in those regions. Usually there was so much snow and wind that you couldn't see at all. But Ruby Lake was determined to explore these areas. It wasn't snowing, after all. Ruby Lake carefully put on her saddlebag and slowly began trotting out of the entrance to her town.
"Hopefully I won't be gone for too long or my citizens will start to worry about me..."
Ruby Lake turned around and looked at her small town. Phew. Everypony was still asleep. She turned around again and braced herself for what could possibly be in the outskirts of Crystaltown.
It took a whopping two hours to make it to a strange cavern. For some strange reason, there were glowing and pulsating lights inside of it.
"What's in here?"
Ruby Lake was scared, confused, and stupefied at the same time. Could something dangerous be waiting for her in there? She didn't want to take any chances, but at the same time she felt brave. So she made the decision to explore the cavern.
Water was dripping off of stalactites as Ruby Lake slowly entered inside of the cavern. Once she gets back from this "short trip", she'd tell her citizens that she discovered a cavern. But what should she call it? Dripping Cavern?
No. That was a stupid name. Keep going.
Ruby Lake slowly trotted in the cave. Too bad she wasn't a crystal unicorn because she needed to see what lied inside this cavern. She could barely see a thing in there.
"Ugh! It's so dark in here! I wish there was some-"
Suddenly, Ruby Lake halted in front of something tall and strange.
"-light."
She had found the cause of the pulsating lights. There were three giant crystals looming in front of her; one gold, one lavender, and one light blue. Why were these crystals here? Were they magically or naturally formed? Why did they glow? Ruby Lake knew the answer to neither of these questions. She had just walked into this cave with nary an idea, after all.
"Celestia, please give me an answer, a sign, as to why these crystals are here in this cavern. I dearly ask you to tell me what is going on."
Ten minutes had passed since Ruby Lake sent her message to the wise Princess Celestia. Perhaps she might know why these crystals are in the cavern.
Suddenly, as if Ruby Lake's question was answered, the cavern began to shake wildly as if something giant was inside. Did a dragon live in this cavern? Apparently not because the crystals began to rapidly shake back and forth as a bright white pulsating light began to flicker in the center of each crystal.
"W-what's going on here?"
These crystals were magically formed after all. The three flickering, pulsating lights soon grew bigger and bigger until it seemed to envelop the crystals. A high-pitched screeching sound that seemed to be emitted from the lights was heard as the crystals began to crack, shatter, and crumble.
After this magical process was finished, Ruby Lake cautiously approached the now-destroyed crystals. In the three huge piles of crystal shards lay three crystal fillies. One light gold filly was in the gold crystal pile. One light lavender filly was in the lavender crystal pile. One alice blue filly was in the light blue crystal pile. They shivered because it was so cold inside the cavern. Why were they fillies? Were they magically formed on purpose? Was this how the first crystal ponies were formed? Why didn't the fillies emerge out of the crystals as foals and not fillies?
Ruby Lake came to the conclusion that these crystal fillies were magically formed and had no real home. But who would take in three magically-formed fillies?
"I'll take you three in."
As the three clueless crystal fillies were told to follow Ruby Lake out of the cavern, she finally had come up with a name for the cavern that she had just explored.
Crystal Filly Cavern.