My first true MLP OC: Daren the Shadow Pony

Daren was born as a sweet, mischevious energetic little unicorn on a rock farm in the middle of nowhere. Ever since he was little, he dreamed of being a brave, virtuous warrior, saving lives and keeping everyone safe. He would always go into the Everfree forest and get himself into trouble.
One day, while he was moving the rocks, his cutie mark appeared. Three small stones sat there on his flank. He was upset and discouraged. He was sure his destiny was to be a warrior. He tore the flesh from his flanks as a sign of rebellion and told his parents that he had just had an accident with the rocks.
When he was old enough, he tried to enlist in the army, but was eventually turned down. After that, he decided to travel from town to town, searching for danger, using his special earth abilities to defeat mighty foes.
For a long time, he felt he had truly become the hero that he had always wanted to be. That is, until he ran into one enemy that he couldn't defeat. It was a large, fire breathing dragon.
His earth powers were useless against the dragon's scales, tougher than the best armor. He was beaten soundly, and that night, he decided that he would defeat that dragon, no matter what the cost.
He studied Magic really hard, getting every spell book he could get his hooves on and memorizing every page, but sadly, his magical power was too limited. Just when he was about to give up, he found a thick, dusty tome in the back of an old abandoned library. It was labeled, "Dark Magic."
He opened the book, and out from the pages shot a powerful evil magic that consumed his sanity mad and turned him into a shadow pony.
Now, he continues to wander from town to town, still trying to become the hero he always wanted to be but often his insanity causes him to hurt others more than help them. He still swears vengeance onto that Dragon, but the dragon has eluded him since he became a Shadow Pony.
Sporting an unsettling smile and a voice that makes even the bravest quake in fear, he travels alone, never letting go of his dreams.