Since ancient times when shiny natural surfaces of water and stone were used, the reflective surface has been used as a focus for occult and/or paranormal activity.
It serves as an important symbol in such literary classics as Dracula, Through the Looking Glass, The Picture of Dorian Gray (with the painting substituting for the mirror), and the fairy tale, 'Sleeping Beauty'.
Mirrors reflect an alternate reality because we do not see 'us' but the reverse of 'us' and this heightens the sense of unreality. Infants think they are seeing another baby in early tests. Mirrors also allow for easy transit into a trance state and have been used to focus physic viewing.
As anyone who has ever gone the, "Bloody Mary" route in the dark in the middle of the night - well they can be down right scary too! The mind is capable of creating anything it can imagine. A child one time said he could roar like a dinosaur and preceded to illustrate the might of his roar, only to have his eyes grow wide, his breathing start to pant, and his skin to pale; he literally frightened himself through the power of his own imagination!
Imagine someone who was intensely 'evil' (what happened to Nero's or Hitler's shaving mirrors as an example?), in great pain, under the influences of some drug, mentally ill or totally insane. Couple this with the ability of the mirrored surface to allow for ease of transit into and through a trance state. The result could be an object infused with an intense amount of energy.
Mirrors can be collectors of energy and doorways to other dimensions in some cultures. Breaking them shatters luck for seven years. Covering them after a death an act of respect but also a protection for the departed soul least it be sucked into another time and place and trapped or become lost.
Since the purpose of the mirror is basically narcissistic, it is easy to see how imbued with personal energy such an object might become. A person would fill the mirror with the energy of their own super-ego and id. Their vanity at their own looks, their fears of loosing it, their self-loathing, or their anxieties at approaching age all there in that surface....
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