Oppositions are at the heart of most fiction. Whether it’s light and dark, good and evil, fish and chips (all right, maybe not that last one), it’s the conflict created by intrinsic oppositions that makes most stories interesting.
That’s why, as an author, it’s important to decide what those oppositions are going to be. One easy way to do it is to ask yourself what your novel is about, when you get right down to it. Please don’t just go into the whole ‘well, it’s about vampires who…’ routine at this point though, because that’s surface stuff. What is it really, deeply about? If you’re not sure, ask yourself what it could come to be about, or what you care about deeply. Court of Dreams, for all the jokes, is about notions of responsibility, duty and family, with the characters reflecting different takes on those themes.
Once you know what your novel is about, it’s easy to build up characters to show the oppositions inherent in your ideas. The danger here is that you think either that the opposition can only be shown by a villain, or that building up ‘opponents’ for your main character means putting in monsters. Neither is true. For the first point, remember that often it is the closest characters to the main one who should reflect different views most strongly, as in the average romance novel, where the major opposition is between the protagonist and his or her eventual intended. Without that conflict between the two over fundamental issues (and it has to go deeper than just ‘I don’t like you that much’) it’s not nearly so much fun.
With the second point, monsters don’t show us much (though see under M, below) they aren’t clever or human in the sense of having a real personality. They aren’t characters forming part of the argument of the novel, they’re just something to hack apart.