Every spirit and to a greater extent every community of spirits has its own aura, formed from and given off by the assumptions and self-deceptions that it has adopted. (Demons have an aura formed by their longings.)
By its inherent nature, when one person’s aura of assumptions and self-deceptions influences another person, it makes truth appear to be false. It also stirs up all kinds of supportive ideas, so that it convinces the person to accept falsity as true and evil as good. (This fact made it clear to me how easily we can become entrenched in falsity and evil, unless we believe the truth that comes from the Lord.) Such auras are denser or thinner, depending on the nature of the falsities.
These auras are completely out of harmony with the auras of spirits who subscribe to the truth. If the two kinds of aura come near each other, war breaks out. If the atmosphere of falsity is permitted to win, the good spirits come into times of trial and anguish.
I also perceived an atmosphere of disbelief, in which people accept nothing that is said and scarcely even what is in plain sight. And I perceived the atmosphere of those who believe nothing but what they can grasp with their senses.
In addition, I saw someone dressed in dark clothing sitting near a mill, apparently milling flour. At his side appeared a little mirror. Later I saw certain products of his disordered imagination, which were surprisingly wispy. I wondered who he was, but he came to me and said that he was the person sitting by the mill and that he had possessed the idea that absolutely everything was simply a hallucination and nothing was real, which is why he ended up in this position.
from Secrets of Heaven, Volume 2, Section 1510