The Frostborn Saga - Book One: Frostfall, by Astral Knight

Felix Frost's world gets turned upside down when a cursed dagger awakens his true form: He is half-human and half-Frost Giant. If that isn't confusing enough, his childhood friend Hilda is a Shield Maiden working for Odin, Lord of the Nine Realms. The ancient adversaries of Odin, Hella and the Frost Giants, want Felix to join their forces to free Hella's son: Loki, the World Eater Serpent, and bring about Ragnarök. Odin needs Felix and Hilda's help to save the Nine Realms and prevent Ragnarök since Felix is the only one who can use the cursed powers of Skaoi's Fang, a cursed dagger and the only weakness of Loki. Yet Felix is torn and does not know who to trust. Hella promises him answers about his father's mysterious death and Odin only wants to use him as a closely guarded tool because of his forbidden heritage. It's a race against time as Felix must learn to use his powers and decide where his loyalties lie. The fate of the Nine realms hangs in the balance!