Oisin is the child of Edad De Brun and Danore De Brun, and heir to the De Brun linage. He is a priest of the Order of Corellon.
Oisin has been estranged from his father since birth, the Baron blaming him and the birth from taking away the one thing he truly loved. He grew up in the arms of the fortress staff until he was old enough to start priesthood training with the Order of Corellon.
He recently had been the victim of an attack by orcs on his way back to Fortress De Brun from Regus. His guards were slaughtered, and he ran injuring himself by falling down a ravine. He was rescued by a party of adventurers on their way through and returned to the De Brun estate.