An ancient, storied evil arrives in Equestria, and joins Fluttershy's menagerie, as a baby dragon.
Will the Mane 6 Discover it in time?
Will they recognize the evil when they see it? Or can it avoid the temptation to succumb to his previous nature?
Will a brave knight challenge this evil with courage and the power of friendship? Helping him face the terror of the memories of his death?

Crossover, but that would give it away.
One Chapter one-shot.
Edit: Fixed several typos, added Alternate Universe tag, and changed the terrible description (to something less terrible, I hope).

Rated Teen for some rather uncomfortable implications.

Definitely a crossover, but spelling it out would be a spoiler. Disclaimer at the end.