Percy Jackson and the Olympians: Legends

Castor, much like Pollux, was described as 'a couple of plump blond boys who looked just like Mr. D', suggesting that they look a lot like Mr. D and may not be as athletic as the other campers. However, it is stated that they are good athletes. The noticeable difference between Mr. D and the twins is the color of their hair. Mr. D has black hair while the twins have blond hair.

Castor was very close to his brother Pollux and loved him. They were always seen working together in the camp. When Castor died, it made Dionysus more protective towards Pollux, Castor's twin. It is revealed that Dionysus actually lived with Castor, Pollux and their mother for a while and enjoyed it.

Years ago, Castor fought bravely for the camp, but dies during the Battle of the Labyrinth by the hands of an enemy demigod (stabbed in the arm and hit on the head). His father Dionysus is depressed and angry over his son's death, surprising everyone at camp by caring about his dearly departed son. At Castor's funeral, his twin brother Pollux tries to make a speech for his brother, but is unable to recite the words, choking due to his grief. Pollux then lights the funeral pyre and sobs.