Castor was the elder twin brother of Polydeuces and part of the Argonauts. Both Castor and Polydeuces had the same mother, Leda, but Polydeuces' father was Zeus, while Castor's father was a mortal man named Tyndareus; because of this, Castor was mortal while Polydeuces was immortal. When Castor died, Polydeuces requested to share his immortality with him, and they became the Gemini constellation.
"A hero in Greek mythology. He is Polydeuces's half-brother, but doesn't share his brother's immortality. He was struck and killed by an arrow, after which he and his brother became stars in the constellation Gemini."
Ken Amada's mother was accidentally killed by Shinjiro during a SEES mission two years ago in 2007. SEES tunnel-visioned on a roaming Shadow they were fighting and consequently did not consider civilians in the area, and Shinjiro lost control of Castor due to inexperience, resulting in a rampage. Castor apparently crushed all of the Amada house. Ken tried to explain what happened to a police officer and Ken described Castor as a "shining horse monster", but the officer didn't believe him. Mitsuru Kirijo apologizes to Ken because her family probably covered up what happened as a car crashing into the house.
Persona Q: Shadow of the Labyrinth[]
After the two Heroes complete the request, The Power of the Wild Card, Margaret explains to everyone how their Personas can now evolve and attain new power. Koromaru and Shinjiro stick around after everyone else is dismissed, and ask if it is possible for them to keep their personas, rather than attaining new ones. Koromaru explains, through Aigis, that he does not want his persona to change so that he can never forget his most important failure; Shinjiro states that his reasons are similar to Koromaru, that he does not want to forget what he has done, and so that "he doesn't lose his way." Margaret tells them that it should be possible for their personas to remain the same if they focus on keeping things the same when they start to attain new power.
Raise defense and protects allies. Extra defense while protecting. (1 row)
Innate
Challenger Arts
Passive
Slightly raise attack against enemies with higher HP.
Innate
Endure
Passive
Survive one lethal attack with 1 HP instead of being KOed.
Innate
Effortless Style
4 SP
Add splash to single-target attack skills for 3 turns.
Evolution
Regenerate 2
Passive
Moderately restore HP at the end of the turn.
30
Vengeful Smash
46 HP
Medium Phys attack to random targets. Stronger for each hit taken. (All enemies)
34
Return from Yomi
Passive
Medium chance of HP restore when near KO.
39
All Guard
9 SP
Raise defense and protects allies. Extra defense while protecting. (Party)
42
Deathbound
73 HP
Heavy Phys attack. (All enemies) Stronger in Boost.
49
Armor Destroyer
52 HP
Immediate heavy Phys attack, lowers target's defense for 1 turn. (1 enemy)
54
Black Spot
62 HP
Heavy Phys attack. (1 enemy) Stronger in Boost.
62
Regenerate 3
Passive
Greatly restore HP at the end of the turn.
65
Vengeful Melee
67 HP
Heavy Phys attack to random targets. Stronger for each hit taken. (All enemies)
69
Gallery[]
Concept artwork of Castor
Concept anime artwork of Castor in Persona 3 The Movie
Castor's Persona 3 The Movie concept design
Castor in battle
Castor briefly appears in Persona 3 Manga to attack Arcana Hermit
Castor in Persona 3 The Movie
Castor out of control
Castor trying to kill Shinjiro
Castor in Persona Q: Shadow of the Labyrinth
Castor glowing in Persona Q: Shadow of the Labyrinth
Castor in Side P3
Trivia[]
Akihiko Sanada's Persona Polydeuces shares some design elements from Castor, namely from his long blond hair and the square materials on his body. Their shoes and gloves look the same as well, with the difference being their color.
The two Persona's similar designs to one another may be a reference to their mythology as being brothers as well as the relationship between Shinjiro and Akihiko.