According to Jung, the shadow, in being instinctive and irrational, is prone to psychological projection, in which a perceived personal inferiority is recognised as a perceived moral deficiency in someone else. Jung writes that if these projections remain hidden, "The projection-making factor (the Shadow archetype) then has a free hand and can realize its object--if it has one--or bring about some other situation characteristic of its power."  These projections insulate and harm individuals by acting as a constantly thickening veil of illusion between the ego and the real world.
From one perspective, 'the shadow...is roughly equivalent to the whole of the Freudian unconscious'; and Jung himself asserted that 'the result of the Freudian method of elucidation is a minute elaboration of man's shadow-side unexampled in any previous age'.
Jung also believed that "in spite of its function as a reservoir for human darkness—or perhaps because of this—the shadow is the seat of creativity."; so that for some, it may be, 'the dark side of his being, his sinister shadow...represents the true spirit of life as against the arid scholar.'
Shadow (psychology) - Wikipedia, the free encyclopedia