Weeping Angels

Weeping Angels are fictional monsters from the "Doctor Who" series, depicted as statues of angels that appear to be stone sculptures. When unobserved, they are animate and move incredibly quickly, but when seen directly, they become immobile and stone-like, effectively "freezing." Their primary ability is to send their victims back in time by touching them, feeding on the potential energy of the life they displace. This combination of invisibility when observed and sudden movement when unobserved creates an unsettling threat, making them a compelling example of a creature that exploits human perception and attention.