Part of realistic consequence in a fantasy setting, is to move away from tradition DnD good vs. evil when it comes to the central character. The twilight hero against the backdrop of light and dark gives an extra dimension to the story and lets the player identify with the protagonist.
In other words, moral dilemmas should be about the character of... the character. And not about the grand fight of light and dark. Choosing to kill someone, for example, should depend on more factors than whether of not you want to be a good guy. To achieve that, a decent motivation is needed. Are you killing him to save other, to get some hard needed coin, because he has done something wrong, because you don't like his face or because he reminds you of a demon you once saw while playing snooker?
