I really, really, really suggest that you don't involve the main character's home being burned down right at the beginning. His girlfriend being killed as well is a little weak. The Dark Guard as well. They're all so clichéd it isn't even funny.

I forgot where I heard the comment, but it stands true. "Whenever I hear about the shadow lord living on mount doom, I can only laugh." Dark lords, dark guards, anything like that is extremely over-used an rehashed. As stated earlier, the same applies to the burning village and loss of a loved one right at the beginning of the story.

As for any suggestions of what could happen, I would suggest to make it deep and thought provoking. Don't make it just some good guy versus bad guy thing. Make your characters and plot believable, but not bland. Things can be interesting without making it insane.

Though, you can go the route of having things make absolutely no sense until it's all tied in at the end and everything makes sense. Confusing your audience will hook them into continuing so that they can understand what's going on.

I like Tomothy's suggestion, myself. Dreams are always a good source of creativity, and his dream isn't lacking in that department. A main character running from someone and he doesn't know why. When he's caught, he learns why he was being chased and has to learn to live with what he did. But before he can do that, he has to escape, go berserk and turn to his dark side.