Mysterious elementary particles that are attracted to consciousness, settling on adults and objects of human workmanship but not on children. The Magisterium considers Dust to be physical evidence of Original Sin. The scientist Mary Malone discovers that Dust is in fact conscious - it is what makes matter aware of itself. Different cultures know Dust by different names: Shadows, Rusakov particles, sraf. The entire plot of the trilogy revolves around the nature of Dust and the Magisterium's attempt to sever the connection between Dust and humanity.