Another of Moffat's incredible creations, the Weeping Angels work amazingly well as a Doctor Who enemy because they are something out of everyday life. You've seen them kneeling over graves at the cemetery. You've seen them in those outdoor statue and antique shops. What you didn't know then is that these are far more than just statues. In fact, they are inter-dimensional hunters and predators with the perfect defense mechanism. They have the ability to “quantum-lock.” Simply put, any time anyone observes them, they turn to solid rock. As such, the only way to survive an angel assault is to stare directly at them and not blink.
These creatures move unfathomably fast, so one blink may be all that separates you from being another unfortunate victim of the angels. These hunters do not want the Doctor dead, they simply hunt to survive. If the Doctor happens to be one of the items on the menu, he will be hunted just like everyone else.
