Meaning "double walker" a doppelganger is a shadow-self
that accompanies every human or a ghostly counterpart of
each person. Only the owner of a doppelganger can see it,
otherwise it is invisible to human eyes.
Dogs and cats have been known to see doppelgangers.
Providing sympathetic company, a doppelganger almost always
stands behind a person, and they cast no reflection in a
mirror. They are prepared to listen and give advice to
humans, either implanting ideas in their heads, or a sort of
osmosis. It is said to be bad luck if it is seen, and rarely
a doppelganger will make itself visible to friends or
family, often causing great confusion. Doppelgangers can be
mischievous and malicious.