The Shadow Isle: Book Three of The Silver Wyrm

Katharine Kerr's Deverry novels tell a complex tale of ancient wrongs and of a timeless vow made to set things right. But it is a vow that will take centuries to fulfill, and the key characters will live through numerous incarnations along the way - for their destinies have been inextricably linked by both powerful dweomer magic and by the debts they own to one another.
With the publication of The Gold Falcon and The Spirit Stone, Books One and Two of The Silver Wyrm, Katharine Kerr began the long-awaited fourth and final cycle of the Deverry chronicles. Now, The Shadow Isle, the third novel in The Silver Wyrm cycle, weaves together many of the story strands of this fantasy masterwork, paving the way for the final volume, The Silver Image.
The wild Northlands hold many secrets, among them the mysterious dweomer island of Haen Marn, the mountain settlements of Dwarveholt, and the fortified city of Cerr Cawnen, built long ago by escaping bondmen from Deverry. thanks to the Horsekin, who continue to push their religious crusade south toward the borders of the kingdom, the human beings of Deverry and their elven allies have realized the fate of the Northlands lies tangled with their own. Although the dwarven race holds strong, the island of Haen Marn has vanished and Cerr Cawnen seems doomed. Only through the magic of Dallandra and Valandario and the intervention of the powerful dragons, Arzosah and Rori, do the allied forces have a hope of mastering the secrets that can save the Northlands and themselves from conquest.