They often have to guard the entrances to the world of the dead , such as graveyards and burial grounds , or do other things related to the afterlife or the supernatural . These might be hunting down lost souls or guarding a supernatural treasure . They are often assigned to guard the entrances to the world of the dead , such as graveyards and burial grounds , or undertake other duties related to the afterlife or the supernatural , such as hunting lost souls or guarding a supernatural treasure .