The opera follows Duncan's banishment from his clan, his relationship with a mortal woman named Aurora who becomes his first wife and his encounters with an Immortal Visigoth named Fritagern from the 17th century to the 21st. In the end, Duncan beheads Fritagern after he murders Duncan's fiancee, a cloned Aurora, on their wedding day. Duncan is portrayed as being tall and brown-haired (usually long and/or in a ponytail). Like all Immortals, his aging process stopped at the moment of his First Death when he was three months away from his 30th birthday. Thus he's been looking like a man in his early thirties for four hundred years and will do so until, if ever, he is beheaded. His injuries heal very quickly and when he is killed by any means other than beheading, he revives some time later fully healthy again. Duncan was raised to be the next chieftain of his clan and this fact influenced his personality. He has a strong moral conscience and a sense of nobility; he protects the weak and innocent and punishes the evildoers. He is known to be very loyal. He is referred to by more than one character as a "Boy Scout" and tends to see things in terms of black and white, being often criticized – sometimes in jest, sometimes not – for his rigid sense of honor and his determination to intervene in events that often place him in danger. He feels responsible for others and when he thinks people died because of him, he feels he has to avenge them. He mentors new Immortals even when he has doubts about them. Like all Immortals, he is unable to have children, but he likes them and takes care of those he meets. Duncan enjoys life. As Connor said, he has "all the fun and most of the good women". Although he has known many women, he shares his life with a few women he grows to love. Those who are mortal, he remains loyal to their memories and cherishes the moments he had with them. He is a perfectionist and keen to learn new things, be it reading, playing Shakespeare or fighting skills (see below). He is cunning and very difficult to defeat in combat because of his skill and because he has experienced most of everything life has to offer. He has a very good memory and can remember things that happened centuries ago. As an Immortal, Duncan takes The Game with a grain of salt. He fulfills his duty and defends his head when he is challenged but he is not bloodthirsty and occasionally spares his opponents, especially female Immortals.