What is this spirit which appears in the fog? Is it approaching you? No, it's just an unusual meteorological phenomenon called a Brocken Spectre. Les Crowley explains at Atmosphere Optics that the image is the viewer's own shadow cast on the mist:
The Brocken Spectre appears when a low sun is behind a climber who is looking downwards into mist from a ridge or peak. The "spectre" is the shadowy figure - the glow and rings are of course a glory centered directly opposite the sun at the antisolar point. But how is the ghostly figure produced? It is no more than the shadow of the climber projected forward through the mist. All shadows converge towards the antisolar point where the glory also shines. The sometimes odd triangular shape is a perspective effect. The Brocken Spectre is a similar effect to anti-crepuscular rays and cloud shadows.