Born in a provincial city in Zofia to a long line of soldiers, Deen underwent his father's rigorous training since youth, joining the Zofian Army when he came of age. Becoming engaged to a feudal lord's daughter, he was set to inherit the lord's peerage. However, while he was away for a mission, the mansion was attacked. As he rushed back upon hearing the news, he himself was attacked and lost his left eye. Reaching the mansion, he found his wife, whose form had completely changed. To kill his beloved fiancee and enact revenge on the man who took his eye, he took the lord's heirloom, the Brave Sword.
Like Sonya, Deen eventually works for Grieth as a member of the Grieth Pirates, despite hating him due to his evil deeds. If Sonya is defeated by Celica, Deen will retreat into Grieth's Citadel. After Grieth's death, he will join Celica's army, noting that he knew that Grieth would have gotten what he deserved eventually. After the war, he vanishes, rumored to have gone to a continent to the south in search of new conflicts.