I think they come from prisons, drug dealers, drug consumers, most from people suffering and living in abuse, stressful situations, vicious situations. I agree with the fellow who said we share our thoughts collectively.
I am sorry if my message does not contribute to this topic, but I just read the message quoted here and asked to myself, is there any books about this topic "nature and types of spirits in daoism and related?".
Maybe someone can help me.