Scripture speaks repeatedly of good and bad angels moving about unseen (Daniel 10:1-21), but also as interacting with living people at different times, even to the point of evil spirits actual possessing people (dwelling within them and controlling them (see Mark 5:1-20, for example). Good angels, on occasion, appear to people as well (Acts 5:17-20; 12:3-11). The four Gospels and the Book of Acts are filled with many incidents of demon possession and of good angels appearing and aiding believers. Angels, both good and bad, can cause unusual natural and supernatural phenomenon to occur (Job 1-2, Revelation 7:1; 8:5; 15:1; 16).