The Raven God (The Legends of Orkney Series, Book #3) by Alane Adams
After defeating the Volgrim witches, life in Orkney is quiet. Too quiet. Before Sam Baron can catch his breath, an army of fire giants led by Surt gather in the Eighth Realm of Musspell, determined to destroy Orkney--and it's all Sam's fault. After all, he took Odin's life with an ancient cursed dagger, and now, mankind has lost its protector. To make matters worse, the God of Mischief, Loki, is on the loose and determined to reunite with his evil wife, Angerboda, and their three children: Fenrir the wolf, Jormungand the sea serpent, and Helva, Goddess of Death. Orkney's only hope lies with Sam and his stalwart friends. As Surt prepares to launch his forces against Orkney, Sam and two of his fellow witches, Perrin and Mavery, set out on a journey to rescue Odin, aided by Skidbladnir, a magical ship of the gods that can fly over land and sea, and Geela, a Valkyrie who can transform into a battle-ready goose. Meanwhile, Leo and Keely travel north to stop Loki from starting a war between the Eifalians and the Vanir, while Howie is left to watch over Skara Brae. With time running out, our heroes try frantically to prove once again that they can find the courage to do what's needed when the odds are stacked against them--even when the sacrifice asked is greater than any of them could imagine.