The second reason is that Casca is one of the most potent reminders that Griffith is not a good person, and that despite appearing to be the messiah, he is a man with dark issuses. We are shown that his actions in the eclipse do have a permenant effect on both Gutts and Casca and that it would be foolish to fully sink into the stary eyed admiration that alot of the citizens of Midland have for him.