Dark Star Rising — Arthur Wiederhold

Young half-Elven Saljanon discovers that his father was murdered on his way home from work and his mother replaced by a shape-shifter. His mother, a princess of the Elven kingdom of Esmendrill, is being held by the hated Dark God Parklathvar in his stronghold of Teufelschloss. Thus begins Saljanon's quest to rescue his mother against terrifying odds and the awesome powers of the Dark God. Along the way, he assembles a band of brave young men and an aging old warrior, who pit their skills and strength against shape-shifters, Troll warriors, zombie soldiers, and Saljanon's own long-lost sister!