The Imperium empasises the power of faith, stating that with the power of faith they may overcome their foes. Sebastian Thor himself said that: "A single man with faith can triumph over a legion of the faithless." Does faith have any useful benefits beyond being useful against daemons? How does faith hurt daemons anyway?

On an unrelated topic: Space Marines aren't meant to have a sex drive, but the Space Wolf Codex states that a wolf lord makes a pass at a woman, while the Space Wolf novels hint at an intimate relationship between Ragnar and a woman. Are the Space Marines capable of sexual desire?