I knew a gal that was possessed. We thought she was saved but apparently not. She got into Ouija board with her sister and her behavior began to slowly change. She went from not feeling like attending church anymore to outright hating God and Christians over the course of about a year. My brother went to pray for her and she fell on the floor and started howling these eery sounds - it did not sound like her voice at all. It sounded like a man's voice. Her hands turned into the hands of a 100 year old woman, gnarled and her fingers twisted around but she was only 40 at the time - those were not her hands and that was not her voice. I worked in healthcare for about 15 years and was around lots of mentally ill people. Their physical appearance and voices did not change in that manner. People with the gift of discernment can usually easily tell the difference between mental illness and evil.