Chamber of Ghosts - Island of Fog, #6

Magic has been nullified by a phoenix. Now shapeshifters are as ordinary as everyone else. But there's hope. To the east lies Bad Rock Gulch where goblins mine for a special kind of energy. This place has a cavern deep underground known as the Chamber of Ghosts where the shapeshifters might be able to replenish their magic - to recharge. Problem is, the chamber is haunted. It's here that Hal receives a warning his life is in danger.
What unfolds changes his perspective on everything he knows, and he soon finds himself alone, trying to persuade his friends to see things his way. Set on a course of action that everyone thinks is foolhardy and dangerous, he's plagued by doubt but resolves to see it through no matter what... With mountain trolls, a village of werewolves, underground ghosts, a boy from the past, and a trio of thundering helicopters carrying a cargo that will change the world, the sixth book in the series literally goes out with a bang.