In the beginning, there was Darkness and then God said, "Let there be Light." And there was Light and it was good. And the The Darkness resented it. And so, in a time before time, an eternal war between Light and Dark began.
Standing in opposition to the chaos represented by a world of Darkness, the totalitarian order and purity represented by the primal force of Light known as the Angelus burns away all life. Just as the Darkness possesses a human host in order to exert its will over the Earth, so does the Angelus assimilate a human body as a vessel with which to concentrate the focus of her power.