People of the light, I bring with me hope and salvation! In the name of Pelor!
Losing all his family at a young age, Corrin left his home to seek meaning in his dismal existence. After many dark nights and near-deaths, Corrin discovered the Light. The god Pelor came to Corrin on what was supposed to be his death bed and offered him a second chance; something no one else had ever offered him. Of course, this chance came with the condition of everlasting devotion to none other than Pelor.
With his only other option being death and the possibility of eternal damnation, Corrin humbled himself before the gracious Pelor and chose a lifetime of service to his new-found savior.
Pelor led him in the ways of righteousness and eventually to the teachings of the Cleric. Corrin spent much of his time simply channeling the divine spirit of light to increase his abilities as a Cleric, but spent all his remaining moments seeking those in need of the Light and righting that which is wrong.
Some time passed, and Corrin somehow came upon a message from the prince of his homeland carrying terrible news: his home had been nearly destroyed! The prince was calling to those still loyal to come and aid the rebuilding and recovery of the kingdom. Corrin had not returned home since he originally left so long ago, but decided, with the Shining One lighting his way, that now was the time to go back. His home was shrouded in darkness, but he knew he could bring the light back with him.