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In this painting, the light is behind the woman on the large creature. The light is solely entered around her. Everyone below her are in the dark. The position of the light makes it seems as if she has descended from heaven in order to defeat some sort of evil on Earth.
Source: http://ec2-79-125-124-178.eu-west-1.compute.amazonaws.com/articles/The-cream-of-the-Old-Masters-crop/26750