In October 12th, 633 AD, the army of the kingdoms of northumbria lead by Edwin, or Æduinus of Northumbria toward the River Don. Waiting for him were the armies of Gwynedd, led by the Briton Cadwallon ap Cadfan and Mercia. By the time the night was upon them the Northumbrian army, tattered, stood mightily above their enemies. The battle was won. It was on to conquer Mercia.
IOTL this was not the case. The armies of Mercians and Brits had overwhelmed them, leaving the king and his heir dead, and leading to the temporary destruction of Northumbria. But this is not the case, and here we enter a world where Æduinus survives