What does everyone think of this story idea?

A boy inhabits a futuristic world inhabitted by people with powers such as fire/water etc, ruled over by a king who strives to master each power and develop the power of shadow to make him invincible. Each of his test subjects for the shadow project dies until he captures the boy after destroying his hometown and murdering its inhabitants, including the boys family. The boy survives the experiment to give him shadow powers and later escapes and goes after the king to avenge his family and free his people.