Here is a series of videos with Spanish exorcist Fr. Jose Antonio Fortea, one of the most knowledgeable people in the world on the topic of exorcism, demonology, and spiritual warfare. This set of interviews inspired the book Interview with an Exorcist, which I would highly recommend: a powerful book filled with information on spiritual warfare, sin, temptation, prayer, psychology and spirituality, possession and deliverance. Also, please check out the fascinating documentary film Exorcist in the 21st Century, which follows Fr. Fortea on his ministry.