Oswald: Return Of The King (Northumbrian Thrones Book 2)
The exiled family of King Æthelfrith of Northumbria arrive, after much hardship, on the island of Iona, where the monastery founded by St Columba has become a center of worship and learning. Amid the violence and turbulence of Dark-Ages Britain, the island appears a sanctuary to the hunted princes and Oswald, having become firm friends with a novice named Aidan, enters the church along with his younger brother, Oswiu.
As befits a young prince, Oswald learns to fight and soon becomes renowned for his courage, earning the title Lamnguin, the Whiteblade. However, the peace of Iona leaves Oswald torn between becoming a monk or returning to Northumbria to reclaim the kingdom that is rightfully his. When news reaches Iona that his half-brother, Eanfrith, has been killed by Cadwallon, the king who defeated Edwin, Oswald sails back to Northumbria and meets Cadwallon in battle, defeating and killing him.
Oswald, now the undisputed king of Northumbria, gives Aidan the island of Lindisfarne as a base from which to take the faith to the English. But Penda, the last great pagan king in England, is raising troops against him.