Castor Troy is the main antagonist of Face/Off.
Internationally infamous terrorist Castor Troy has one weakness: His younger brother Pollux a young blond boy who wears glasses and usually wears shoelaces untied, and perhaps the only person to whom he shows affection. Not to mention he's got to be in his mid-20s and yet he sycophantically follows his brother's every move, incapable of even tying his shoes.
Castor accidentally shoots Sean Archer's son in an attempt to kill him. Years later, Castor plans to activate a bomb in Los Angeles, but Archer successfully catches up with him and Pollux. After a firefight, Pollux is arrested and Castor is knocked unconscious, leaving Archer with no valid information as to the whereabouts of the bomb. Later on, Archer is told that there is a way to find out, by switching identities with Castor in order to extract the information from the imprisoned Pollux. Archer reluctantly agrees and undergoes the transformation by having his face switched with Castor's. However, Castor soon awakens from his coma and manages to steal Archer's identity. He burns Archer's friends, along with the evidence that proves who the real Archer is and takes over his work and family life. He also uses Archer's position to free Pollux from prison.
Eventually, Castor finds out that Archer has escaped from prison and is becoming socially involved with his terrorist associates. Castor and Archer face rack other again and engage in another firefight, with Pollux eventually falling to his death, with his brother dead on the floor, bends down and ties his shoelaces as it used to do before. Castor later kills the head of the FBI and sets a trap for Archer and an associate named Sasha, at his funeral. Castor tries to escape from Archer but he pursues him in a speedboat, and as the pair fight, the boat crashes into a dock and the pair lands on the sand, battered and exhausted. Castor suddenly attacks Archer but he grabs a harpoon gun lying nearby and points it at the terrorist. Knowing he's been beaten, Castor begins to gruesomely slice his own face in an attempt to prevent Archer from ever taking it back, but Archer finally kills him by firing a harpoon into his chest. Archer is then able to take back his own identity as well as a changed life.