Just as there are physical pathogens like bacteria, viruses, and parasites, so are there nonphysical pathogens in the form of etheric parasites, discarnate humans, aliens and demonic beings that can attach themselves to a living person, drain their energy and influence their thoughts, feelings, and personality.
The present situation is analogous to how several centuries ago society knew nothing of physical pathogens and the bacterial and viral origins of disease. They fell ill and knew neither the cause nor medical remedy. Likewise, today people get attachments and know neither the cause nor remedy.
Etheric parasites are negative thoughtforms, which are temporary beings generated in the etheric plane. The etheric plane is a nonphysical substructure underlying our material reality. Etheric energies and constructs are invisible “metadata” that can influence physical events at the quantum level. In occultism they are also called tulpas, egregores, or larvae.
Etheric parasites are generated by human thoughts infused with emotion and intent. This creates an energetic construct in the ether akin to an eddy in a river but imbued with artificial intelligence and purpose. Its most common purpose is to continue its own survival by feeding off the same kinds of energy that gave rise to it. If it was generated through hate, it will induce hateful thoughts in its host to suckle more emotional energy of that type.
These thoughtforms float around in the ether, which interpenetrates and underlies physical space, and can influence the thoughts and emotions of people onto whom they latch. Thus the negative thoughtforms generated by one person can induce negativity in another, proving they are not just internal subconscious subroutines. Occultists know how to create these intentionally, or to produce other effects in the ether, in order to consciously influence the mind of another person. But most thoughtforms are created unwittingly by our everyday sparks of emotion, fantasies, and moments of ill intent.