The sacrifices made by Costigan are so revealing to the audience because it shows this other side of our legal system that surprises many. Although the character is very unreadable, for some reason throughout the film you root for this character because of his courage and strength. This character also brings a very interesting aspect of freedom. The character is free to the extent that he is not held back by the police when he is an undercover police officer. It's almost as if he has an excuse because of his situation to kill and break the law in order to protect his identity. I think that's what makes this character so compelling is that he doesn't follow those typical hero types. Costigan is a mix of good and bad but overall he is a hero who is sometimes confusing when working with the villains and spending most of his time with them. Although Ray defines heroes according to these two categorized stereotypes, Costigan is a whole new subgenre in which he could fit into both the official hero and the outlaw hero, which overall is very captivating as an audience.