The Broken Kingdom — Angus Donald

Post-Roman Britain. Thousands of desperate Saxon refugees are flooding the island, fleeing their homelands as the whole world warms and the waters rise, and worse, the mighty dragon Cythraul from the once-frozen North has been awoken by an evil sorceress. His lust for human flesh is insatiable, and he threatens to extinguish all human life. The land is riven with strife and warfare. The petty kingdoms battle constantly with each other for supremacy and only one man, a young Dumnonian warrior, can hope to unite them. His name is Arthur.