Oswald was king of Northumbria from 634 to 642. After defeating Cadwallon of Gwynedd at Heavenfield, he restored Northumbrian power and invited Aidan from Iona to establish the monastery of Lindisfarne. He was killed by Penda of Mercia at Maserfield and was soon honoured as a Christian saint and martyr.
Oswald’s alliance with the monastery of Iona helped establish Christianity more firmly in Northumbria, with Aidan founding the episcopal centre at Lindisfarne. Bede later portrayed Oswald as a model Christian king whose military success and generosity served religious purposes. He was killed by the Mercian king Penda at Maserfield in 642, after which a cult rapidly developed around his relics and memory.
In M J Porter’s Pagan King, The year is AD641, and the great Oswald of Northumbria, bretwalda over England, must battle against an alliance of the old Britons and the Saxons led by Penda of the Hwicce, the victor of Hæ∂feld nine years before, the only Saxon leader seemingly immune to Oswald's beguiling talk of the new Christianity spreading through England from both the north and the south. In Nicola Griffith’s Menewood, The novel dramatizes the destruction of Edwin’s Northumbrian supremacy at the Battle of Hatfield Chase and the campaigns associated with Penda of Mercia and Cadwallon ap Cadfan.