Tobias Eaton

Tobias 'Four' Eaton is a member of Dauntless who serves as an instructor to initiates transferring into the faction. Born in Abnegation to Marcus Eaton and Evelyn Johnson, he chose Dauntless at his Choosing Ceremony to escape his abusive father, who struck him with a belt. He has dark blue eyes, dark brown hair, a scar on his chin, and freckles on his nose. His nickname 'Four' comes from his instructor Amar because he has only four fears: heights, the dark, claustrophobia, and his father.

He bears tattoos of each faction's symbol on his spine, starting with Dauntless at the top, then Abnegation, then Erudite, then Amity, then Candor at the bottom. In Four: A Divergent Story Collection, it is revealed that as a 16-year-old he discovered he was Divergent after escaping simulation serum unorthodoxly; he befriended initiates Zeke and Shauna, developed a rivalry with Eric, and refused an offer to become a future leader of Dauntless to instead become an instructor.

In the main series, set two years later, he helps Tris Prior through initiation, protects her from threats, and is captured by Erudite where he is injected with a mind-control serum that forces him to attack Tris until she breaks his control. He escapes with Tris, Caleb, Marcus, and Peter to Amity, then joins the factionless camp where he reunites with his mother Evelyn. In Candor, under truth serum, he reveals his reason for joining Dauntless. After Eric is sentenced to death by a new leadership group including Four, Tori, and Harrison, Four executes him.

He later agrees with the factionless to destroy Erudite and establish a new government. When Tris decides to sacrifice herself to save Dauntless members from a simulation, he surrenders himself to Erudite but escapes with her and Peter.