The Snow-Walker's Son - The Snow-Walker Trilogy, Book 1 (Unabridged‪)‬

From icy realms beyond the edge of the world came the Snow-Walker Gudrun, her sorcery bringing tyranny and fear to the Jarl's people. All hope of restoring the true Jarl to his throne seems lost.
In the first part of a trilogy of enchantment, a terrifying journey into exile takes Jessa to the ruined fortress of Thrasirshall. Inside, say the rumours, is a dark menace kept hidden from the world, the Snow-Walker's own son.