The origins of our adversary, Satan the Devil, and his host of fallen angels or demons. God has promised us protection if we yield to and obey Him.
Charles Whitaker, reflecting on a childhood desire of becoming invisible as well as porous, enabling him to get away with all kinds of things without consequences, explains how he was dispossessed of this notion by a wise grandmother. God's invisibility is quite a different matter. People cannot see God in a physical sense, but …
Most of Protestant and Catholic theology is immersed in pagan concepts of hell, reinforced by Dante's Inferno. Here is what the Bible says, without tradition.
The numerous scriptural references to angelic beings indicate that the spiritual entities have tangible substance. God is not a universal nothingness.