Hawthorne states that Aylmer "was not slow in making the birthmark a fearful object, causing him more trouble and horror than ever the beauty, the climate of the soul, or the senses of Georgiana" (Hawthorne) because it was “the symbol of his wife's responsibility to sin, pain, decay and death” (Hawthorne). But we can see from the beginning of the story that Georgiana didn't see the birthmark that way, she saw it as some sort of talisman. Hawthorne shows us here that these are Aylmer's feelings that he externalized onto the birthmark. And as we can see from the end of the story, Hawthorne states that "the fatal hand had wrestled with the mystery of life, and was the bond by which an angelic spirit was kept in union with a moral structure" (Hawthorne). I think this makes it pretty clear that the birthmark was the imprint left on Georgiana by the hand of God when she was created in His image, and that's why it was so scary