The sacrifices Costigan makes are eye-opening for the audience because it shows this other side of our legal system that surprises many. Even though the character is unreadable, for some reason in the film you root for this character because of his courage and strength. This character also provides a very interesting aspect of freedom. The character is free enough to not be detained by law enforcement when he is an undercover cop. It's almost as if he has an excuse because of his situation to kill and go against the legal system as a way to protect his identity. I think what makes this character so endearing is that he doesn't follow these typical hero types. Costigan is a mix of good and bad, but overall he is a hero who is sometimes confusing when he works with the bad guys and spends most of his time with them. Although Ray defines heroes in these two categorized stereotypes, Costigan is a completely new subgenre where he could fit both the official hero and the outlaw hero, which overall is very appealing as an audience.