A King to his Throne

The Crystal Empire was a kingdom of good will, with the Crystal Heart being a conductor of positive emotions for the entirety of Equestria, it had to be.
But of course, with the Crystal Empire being the one with such power over all of Equestria, it was bound to bring in those who wished to control this power.

King Sombra was not the first to try his rule over the Kingdom, though he was the only one to be successful. He was a tyrant, the ruler of an Empire that all had to fear, and for the most part, actually quite clever.
He liked to play games and tricks, with laying trappings all over his kingdom for the heros who wished to take his reign away from him, with making sure that games were played with the citizens he had control, and making sure that all plans he wished to keep were safely hidden away from any of the enemies he acquired as being the Crystal Tyrant. Of course, all this work did not help him in the end.

The Solar Sisters were the ones that placed an end to the Crystal Tyrant’s reign, with Princess Celestia and Princess Luna banishing the King to the Nightmares.
But even though they had banished him, a clever trap that King Sombra had laid was unleashed, and the Crystal Empire was lost to Equestria.

And in turn, Equestria had lost it’s Heart.

The Shadows are all that live in the icy tundra where the Kingdom once stood tall, the Nightmares whisper in those shadows, calling to ponies to come join their ranks and join their army.
Soon rumours and high tales were all that were left to be a sign of the Kingdom that once stood in the snow. With no crystal pony to have escape the trap the King laid, the only evidence that the Crystal Empire had ever existed was from old mare tales and the occasional crystal used for decoration.
The Solar sisters themselves are nearly legends, as they have long since been dead, and only the foundations of society and their respective glass windows in the Canterlot Castle is what remains of them.

But of course, with any high tale or legend, or with any lost treasure that needs to be found, there will always be one to take the role of an adventurer.
A young stallion who went by Starswirl, a young unicorn magician who had a thirst for knowledge, he was the one who had taken upon himself to try and find the lost heart of Equestria.