"Can I tell you something, if you promise not to tell another soul? I'm not a.. hammer, as you say. I have questions. I have doubts. I don't know what is right and what is wrong anymore."
Castiel is an angel of the Lord and has been around for a long time. His age or length of existence is never stated, but he tells Dean that he knew Luke, so it's assumed like other angels, his past goes into biblical history. When Dean was killed and sent to hell, it was Castiel who brought him back. Dean bears the mark of Castiel's hand imprint burned onto his right shoulder as evidence that an angel raised him from perdition.
Believing it was his heavenly mission, Castiel followed orders, which included deeds like purging towns for a greater good and asking Dean to torture a demon to get information. Castiel began to doubt his orders and eventually decided it was morally wrong. For a long time, he was conflicted about what he should do. Anna, another angel who had fallen from heaven, tried to convince Castiel that he needed to listen to his own conscience, but unprepared to take that step, he turned Anna in, an act he would later regret.
Eventually, Castiel decided to help Dean, but before he could speak to Dean on the matter, he was ambushed by other angels at the meeting place he had arranged and dragged back to heaven. Castiel was gone. What remained was Castiel’s vessel, Jimmy Novak. When Jimmy’s family was kidnapped by demons and Jimmy’s own wife was possessed, she shot Jimmy, who would’ve died of the bullet, except Castiel returned, taking possession of Jimmy's daughter, Claire. Through Claire, Castiel destroyed the demons and granted Jimmy’s request of making him Castiel’s permanent vessel, rather than taking Claire.
What happened while Castiel was in heaven? He says later that he experienced first-hand heaven's methods of 'persuasion'. Those methods were terrifying enough to put the fear of God into the angel, so to speak, and remind him of the power of his superiors. He became colder and more distant toward Dean, but Dean could tell that Castiel was behaving that way because he was being bullied. As the time of the apocalypse arrived, Castiel spoke with Dean alone, giving his apology to Dean for letting things come to an end the way they did. Dean would not accept the apology however, and gave Castiel words that inspired a renewed courage within him. Even if it meant dying, Castiel learned there were some things that were worth dying for. He became resolved to do the right thing for a change.
This resulted in his rebellion when he helped Dean escape Zachariah, Castiel's superior and the angel holding Dean prisoner, to help Dean stop the apocalypse. For his betrayal, he was killed by the archangel Raphael and later resurrected by an unknown power.
As an angel of the Lord, Castiel has a strong faith in God. In the Supernatural universe, even the angels themselves seem to have the impression that God has abandoned them, but amidst everything that’s going on, Castiel refuses to believe it. This is the side of him that expresses his undying loyalty. This loyalty is very present, not only during his mission to search for God, but also when it comes to his friends, Sam and Dean. Castiel is willing to fight the armies of heaven for them, use his powers to help them, kill his own brothers for them, and even die for them if necessary.
As an angel, his emotions tend to be far more reserved than the humans he hangs around with. Castiel does experience emotions at times, and it becomes more evident the longer he’s separated from heaven. Castiel doesn’t let his emotions get in the way when it comes to seeing the big picture. For instance, he was willing to try and take a child’s life if that child was going to be the anti-christ, no matter how innocent the child really was about the situation he was in. The thought of killing a child wasn’t something he wanted to do, but he was willing to do what had to be done. There is a weakness in Castiel’s resolve though, and that has to do with his friends. He wasn’t willing to let Anna kill Sam, even if killing Sam would solve the problems. Because of his personal attachment to Sam, Cas shows some bias after all.
Aside from his faith, Castiel has other facets to his personality. He’s innocently quirky, which is amusing to see in the series. Once he’s cut from heaven, his exposure to humanity and Dean’s friendship in particular shapes him a great deal. Although there are doubts, questions, and fears about what he has done, having Dean as a friend and a mission to complete gives him strength. He’s sometimes peculiar in his actions because behaving ‘human’ is, naturally, foreign to him. There are a lot of things about humanity that he doesn’t fully understand, like lying for instance, so there is some stumbling through situations because of his angel tendencies and his new found personal will and conscience.
As an angel, Castiel has many abilities. Rather than make this page really log explaining them… here is a source.
Important relationships and connections.