Paul Kearney: The Second Empire [2001] paperback

Winter lies cold and dark upon the world; it seems that spring will never come. Once dismissed as the ravings of a crazed hermit, the prophecies of Honorius seem at last to be coming true. In the harbour of Old Abrusio, the Gabrian Osprey lies docked at last, home from her long voyaging. Only a handful of shocked survivors remain of that proud expedition that set forward almost a year before ...but they are not alone. Something has come with them from the uttermost west.