When the evil King Gaius announces that a road is to be built into the Forbidden Mountains, formally linking all of Mytica together, he sets off a chain of events that will forever change the face of this land, forcing Cleo the dethroned princess, Magnus the reluctant heir, Lucia the haunted sorceress, and Jonas the desperate rebel to take steps they never could have imagined.

Burdened with the dark, dangerous, and seemingly impossible task of locating and destroying Voldemort's remaining Horcruxes, Harry, feeling alone and uncertain about his future, struggles to find the inner strength he needs to follow the path set out before him.

"Thor's hammer is missing again. The thunder god has a disturbing habit of misplacing his weapon--the mightiest force in the Nine Worlds. But this time the hammer isn't just lost, it has fallen into enemy hands. If Magnus Chase and his friends can't retrieve the hammer quickly, the mortal worlds will be defenseless against an onslaught of giants. Ragnarok will begin. The Nine Worlds will burn. Unfortunately, the only person who can broker a deal for...

While Cleo sets aside her feelings about Magnus to fulfill her royal duties, a betrayed Lucia teams up with a vengeful Fire god; Jonas becomes a pawn in the hunt for the Kindred; and King Gaius sails across the Silver Sea to forge a dubious alliance.