Castor

Castor was a Greek Greek demigod son of Dionysus and the twin brother of Pollux. He was killed in the Battle of the Labyrinth.

The Lightning Thief
Castor is first mentioned by Percy Jackson. He is seen first with his brother helping the strawberry plants grow, then at dinner he is seen at table 12. Percy notices that Dionysus only has two boys in his cabin, Castor and his twin brother Pollux. However, their names are not yet mentioned.

The Battle of the Labyrinth
Castor fights bravely for the camp, but dies during the Battle of the Labyrinth by the hands of an enemy half-blood (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 choke out the words due to his grief as he was crying. He then lights the funeral pyre and sobs.

The Last Olympian
In Percy's vision, Dionysus states that he had already lost one son (Castor) and didn't want to lose another one, and asks Percy to keep Pollux safe.

Appearance
Castor is described to be very good-looking, with slightly curly blond hair, violet-colored eyes, just like his twin brother, Pollux, even though Dionysus had black hair and purple-colored eyes. He is described to have an atheletic look, just like Pollux.

Abilities
Castor presumably has the ability to control the states of the mind, and control grapes and strawberry plants, just like his father, Dionysus. This ability is called Chlorokinesis.

Relationship with Pollux
It is shown that they were very close, and that they loved each other. Pollux was brokenhearted at his brother's death, and this helped his fury against Kronos and his monsters, so he had no doubts about him fighting for his brother's memory. They are always seen working together in the camp. Percy is also sad that he never really got to know Castor before he died as stated at the end of The Battle of Labyrinth.

Trivia

 * He and his brother are named after the Gemini; Castor and Pollux.
 * Like in most versions of the story of the Gemini, Castor dies, but unlike those stories, there are no known attempts to either restore him to life or reunite them.
 * Interestingly enough in mythology, the original Castor was killed while the original Pollux lived.
 * In the solar system, both Pollux and Castor are stars and both in the constellation Gemini, the twins.
 * In ancient Rome, Castor and Pollux had one of the greatest temples, located right in the center of the city.