Walled City by Elizabeth Pewsey
looking for Ivar's bones is the first task demanded on Scarlet when, fleeing through an arched doorway, she finds herself in the Walled City of soothsayers, outside time and the world she knows. Not until the end of a nightmare journey does she understand why she alone can release the mysterious prisoner from Uthar's power and save the countries of Tuan and Vermoria from chaos and final destruction. The last story in the trilogy which began with The talking head and continued in the Dewstone quest.