In the Beginning
Castiel sends Dean back 1973 to meet his parents when they were young. The purpose of this was to show Dean the truth of what happened with Mary Winchester and Azazel. Castiel explains that the angels still have no idea what Azazels endgame is. He then tells Dean that Sam is headed down a dangerous road and that if Dean doesnt stop him, the angels will. 4.07 Its the Great Pumpkin, Sam Winchester. Dean and Sam return to their motel room to find Castiel and Uriel waiting. Sam is thrilled to meet Castiel. Castiels response is to acknowledge Sam as the "boy with the demon blood" and says that he is glad Sam is no longer using his powers. Castiel reveals they found a hex bag, which wouldve killed the boys, secreted in the room. He then tells them that the raising of Samhain by the witch will break another of the 66 Seals. He advises Sam and Dean to leave town because he and Uriel are going to destroy it. Sam and Dean argue that they can find and kill the witch and stop the summoning of Samhain. Later Uriel expresses his contempt for humans and tries to persuade Castiel that they should destroy the town anyway. Castiel reminds him that Dean was saved because he has "potential," and reminds Uriel that they must follow their "true orders." After Sam has used his powers to send Samhain to Hell, Castiel appears to Dean. He reveals that their true orders were to follow Deans decision, as a test under battlefield conditions. Dean, thinking hes failed, asserts that hed make the same decisions all over again if he had to, because of what he and Sam have saved. Castiel confides that he was praying Dean would choose as he did, and that he respects and loves humans as Gods creations. He also admits that he has doubts about the plan from Heaven, and is no longer sure what is right and what is wrong. He warns that in the coming months, there will be more hard decisions for Dean -- and the angel does not envy him that.
After his second resurrection by God, with enhanced abilities, he sees his decisions and support of freewill to have been affirmed. Castiel begins to show pride, while remaining somewhat naive with regard to consequences. Crowley is able manipulate this budding sense of pride to get Castiel to start the angelic civil war. Castiel becomes dedicated to his own decisions, and tends to pass over other opinions, even Deans, in the absence of another clear course. He eventually double-crosses Crowley, taking in the souls of Purgatory alone. He then insists on worship from his former friends. He intends to be an involved god, a better and loving god who will not abandon the world. He renounces his dedication to free will, saying that angels need a firm hand. He is quick to smite those he feels to be hypocritical and unjust, and rewards those who have faith. However, Castiel is being influenced by entities inside him - including leviathans - and his actions become erratic and violent. He realizes he is not strong enough to contain the power, and at a prompt from Sam, he goes to the brothers for help. He is apologetic and humbled; after the souls are out of him he wants to find a way to redeem himself before the brothers. He eventually takes Sams madness on himself, freeing Sam. In episode 5.14 My Bloody Valentine, Castiel shows his deep affection towards raw meat, eating it in the room and unable to get to famine, one of the four horsemen. Here, we realize that Castiels vessel, Jimmy Novak is desiring the food which he cannot gain access to with the angel possessing him. Castiels insanity after taking on Sams memories of Hell seems to free him of some of his guilt, though it leaves his mind scattered. He was unwilling to fight due to his belief that he is a "jinx," though Dean convinces him to help kill Dick Roman. He also expresses some fondness for Meg despite the previous animosity that existed between them. However, after getting trapped in Purgatory, Castiel seemed to have regained his sanity, though he admitted there is no way to know for sure. However, his experiences have changed his personality somewhat and he is no longer as aloof as he usually is and has displayed a fondness for human things he took for granted such as watching television, which he never understood before. 4.01 Lazarus Rising.