Riff has a neato background. He grew up a thief... until one day he robbed the wrong house and wound up with a curse/blessing. From that point on, he could visit other people's dreams.

There were several catches, of course. He is unable to have his own dreams, and when in the dreams of others, he has no control. (They're not his dreams, so they're not his to control.) He eventually went insane. On the other hand, it's a great way to learn someone's dirty little secrets...