Beatrice "Tris" Prior is a young woman who changes from her original faction, Abnegation, to join the more action-centric Dauntless. Because of her upbringing, Tris finds that she knows little about herself when she begins the Dauntless initiation. As the story progresses, Tris discovers that she is proud, courageous, and sometimes even selfless, but she struggles with fears of intimacy and helplessness. She never had any friends in her childhood and has no experience forming relationships with people outside her family.
Tobias, or "Four" as most Dauntless know him, is an 18-year-old Dauntless member who is in charge of training new initiates. He is tough and often harsh on the initiates but believes in the original spirit of the Dauntless faction. Four represents the part of Dauntless that still believes in bravery for the sake of protecting others and creating a better world. Four was abused by his father, Marcus, and though he has strong Abnegation qualities, he left Abnegation to get away from his father. The nickname "Four" comes from Tobias's fear landscape, which reveals that he only has four fears. This is an unheard-of, remarkably low number among the Dauntless.