caster

 class: Caster
 real name: Medea
 measurements: 163cm (height), 51kg (weight), 82cm, 57cm, 84cm.
 colour: purple.
 natural enemies: Berserker.
 likes: plotting, sincere people, men with ambitions but honest
 dislikes: rude people, violent people
 master: Kuzuki Souichirou
 weapon: Her magic and a special knife.
standing: Neutral evil.
noble phantasms: caster has only one noble phantasm, which is anyway pretty effective.
- Rule Breaker - All Code Must Be Destroyed (her knife allows her to break the contract between a  Master and a Servant by just stabbing one of them).

personality: Caster could appear as an evil servant, but she's instead looking for something that can rehabilitate her past. She finds a solution in loving Souchirou and dedicating her existence to him, although she wasn't especting anythign back at all. She was just happy to feel something she had never experienced before. Despite her not properly good intentions, we can't say she's completely bad. She's a character moving towards the dark side, maybe because of her past, maybe because she was only wishing to realize her expectations (that are still a mistery at least in the game and in the manga although it's probably due to her needs to be love and to love someone else). Caster is a sad and tragic character, not to be associated with a pure, evil minded and cold-hearted clichè.

spoilers warning!!!

personal history: Caster was summoned by a Magician of the Association, but due to the bad treatment she was receiving by him she killed him in order to survive. She was risking to disappear because of the lackness of a Master providing her mana, but she luckilly met Souichirou Kuzumi and became his servant. She slowly started to feel affection for this man with a dark past and made hers his dreams and expectations, until she fell in love with him. In Fate she's working by herself, making a contract with an other servant (Assassin) in order to win the war as soon as possible and grant her own true wish before disappeiring, but she's easilly defeated by Gilgamesh, as soon as she tries to get rid of the other masters.
In the second scenario she's working for Souichirou because she loves him and she could do anythign for him. She is killed by Archer in the attempt of defending her master from the enemy's attack. Her death is pretty sad, especially because of the words, full of love and sorrows, she tells to Souichirou before disappeiring.
In the last scenario she doesn't play an effective role and she's easilly defeated with no mercy. She's anyway more lucky in Hollow Ataraxia, as she actually plays the role as Souchirou's wife, being a responsible spouse and a good example for all the other girls, especially Sakura.

the legend behind:In Greek mythology, Medea was the daughter of King Aeetes of Colchis (now a territory of modern Georgia), niece of Circe, and later wife to Jason. I can't deny that Medea is one of the most beautiful characters in the myths and that she inspired many authors, poets and musicians because of her tragedy.
Medea had similar powers to those of Circe and she was somehow "recruited" by the gods to help Jason in his quest to claim the Golden Fleece. She fell in love with Jason and she helped him in coming back home. As they were back to Iolco, her first though was the one to eliminate Pelia who usurpated Jason's throne. With a mischevious plan she was able to succede and she let Pelia's daughter kill their own father (she showed them a sort of spell that was able to give back youth and that instead killed him). Anyway due to her operate, both Jason than Medea had to flee to Efira. They lived there for some years togheter with their children, but Jason badly wanted to take back his kingdom and at the end he accepted Creonte's offer to come back and marry Glauce, his daughter. He abandoned Medea, who immediately felt anger against him and wanted to take her revenge. She sends to Glauce a gift for her wedding: a cape which is majorly poisoned and that kills her giving her infinite pain. Creonte touches the cape and dies too.
Medea also kills her own sons, to eliminate Jason's descendance, and due to this happening Jason commits suicide.
Medea moved to Athens were she married Aegeo and gave birth to Medo. She lived peacefully there until Teseo's return: she felt worried for Medo since Teseo was claiming the throne, so she convinced his husband to kill the impostor. But Aegeo realized Medea was controlling him and he didn't took action against the right heir.
Medea had to flee again and coming back to Colchis she rejoined her father's court.