- Caring. Castiel used to be like every other other Angel, who aren't exactly known for having a broad range of emotions - or any emotions at all. However during his time among humans he has slowly developed an appreciation for them and has come to care deeply for them - the Winchester brothers in particular.
One of his brothers once said that Castiel's problem was that he had too much heart. He cares so much that he will willing throw himself in the line of fire so that others can survive. The proof is in the fact that time and time again he has in fact died, only to be brought back to continue his mission to protect and fight against those that threaten the things he cares about.
- Knowledge. Given that he is billions of years old and was witness to the birth of the planet, Castiel has a vast knowledge of a number of subjects. He can easily tell you a time and place in history without needing to look it up. Maths problems are solved quickly and accurately. His knowledge of languages is practically unmatched as well as his ability to recite a huge amount of supernatural lore after only skimming a textbook once.
However, his knowledge is extremely analytical and despite being on Earth a number of years, there are still things like social cues and innuendo that escape the angel's knowledge. Castiel does pick up things quickly, for instance, he has recently learned emoticons and thus every text is filled with them.
- Loyal. Despite betraying Heaven at one stage and going behind Dean and Sam's back at another, Castiel is extremely loyal. It's not necessarily to any one thing but rather any number of things he feels strongly about. If Cas strongly believes that what he is doing is for the good of the world, then he will remain loyal to the cause and disregard any warning that it could harm him or make a sacrifice.
- Blunt. Castiel is generally a very blunt and direct being. This is where having some knowledge about social cues would come in handy. He is learning but considering his teachers are Sam and Dean Winchester, he might never be able to understand normal social behaviors.
His bluntness, however, does have it's good points, in that he doesn't tend to beat around the bush when delivering a message. And he tends to call others out when they don't get to the point quick enough.
- Self-Critical. While some claim it is a positive trait, it's not in Castiel's case. He takes the self-criticism to the extreme and often has bouts of feeling worthless and useless. At one point, he believed himself to be completely useless in the fight against the Darkness that he sacrificed himself to let someone else use his vessel in an effort to gain more power.
He also takes a lot of outside criticism to heart and often plays it over in his mind so it warps into his opinion of himself. It is a dangerous way of thinking but he just needs reminding every so often that he is good just the way he is.
- Well-Meaning. Just about everything Castiel does is for someone else, vary rarely does he take something for himself. He tries to help where ever he can but sometimes his help can lead to an even bigger problem.
There is also the fact that his good intentions can sometimes lead to dangerous consequences for himself, including death. Unfortunately for his own well-being, Castiel doesn't care. He would die a thousand times and give up his grace again if it meant keeping those he cares about safe. But despite his intentions being well-meaning, he forgets the fact that others care what happens to him.
ABILITY
SECOND LINE.