The Lost Prince of Underworld

The story of a boy who's lost for a very long period of time. War has begun, their throne is losing it's side, he's the only one who can save the realm from destruction. Underworld, a dark, fiery place where souls of mortals and demigods goes when they die. Will he accpet his fate being the lost Prince? Or he'll just run away and let the underworld crumble into ruins?