 Both Mab and Demonreach refer to the spirit as a parasite, knowing that it will enter the world with a great deal of knowledge and power but no experience, judgment, or morals to guide it in their use.As the spirit grows, it begins to put increasing strain on Harry's mind, causing him to experience severe headaches, fatigue, and dulled mental focus.At the end of the novel, Molly safely removes the spirit from Harry's mind and transfers it to a wooden skull he had carved to serve as a backup vessel for Bob.