The missionary Patrick brought the gospel from Christian England in the 300s AD, at the time a province of the Roman Empire, to pagan Ireland. Centuries later, Ireland brought the gospel back to England, where the church had been nearly destroyed by the Saxon invaders of the conquered Roman province. Monasteries were established on the islands of Lindisfarne (east coast) and Iona (west coast). I have visited both islands and enjoyed imagining the fiery missionary monks zealously proclaiming the gospel to pagan audiences. By the late 700s AD, a new group of pagans, the Vikings from Norway, Sweden, and Denmark, were attacking Ireland and England.
All this is to help you picture the historical background of Beorn the Proud by Madeleine Polland, a historical novel for middle school readers set squarely in this time, in the 9th century or 800s AD. Beorn, a Viking boy who participates in his father’s raid on an Irish village, becomes the owner of Ness, a Christian Irish girl captured in the raid and enslaved. His interactions with her Christian character and faith change him, but this has profound implications for Beorn in the pagan Viking society, which values fighting strength and martial gods above all and has little sympathy, at that time, for the more peaceful, true faith of Christianity. How this all works out for Beorn and Ness makes for a compelling story.