History and research have proven that there are powers and forces beyond the physical. No matter what aspect of science seems to deny the existence of the beyond. In a series of research on the occult and demonology, Benjamin Lee reported findings of several years of research, he reported the common powers (aka forces) known and seen among humans. They are the
• Subterranean power, including ghosts of dead persons
• terranean forces, such as an eye for evil
• Aerial territorial powers, including elves and demons,
• heavenly powers, such as the stars and reference to gods.
Although different people of faith may not share the same classification, all these elements are what are mostly found in humans. Based on their influence and effects on humans, they are often categorized as good powers and bad powers. There aren't specific powers tagged "good" or "bad", they are classified either, based on what they do for the general benefits of humans or their harm.
Being the most supreme creation on the earth, humans' bodies are usually the most prevalent places to see the manifestations of these powers, and ease of interaction makes it easier to address them. These powers have always found expressions in different parts of the human body, including the mind, hands, stomach, and the eyes especially. You have probably seen them in movies where these things are portrayed. Well, the video narrations are fictional, they are an offset of a reality that has lived with humans for many thousands of years. It was Emerson who said, "When God created the universe, he set in motion the two great lights. When he created man, he placed in him two eyes." The eyes have been a vehicle for humans' data collection and processing. Humans see by the eyes, send the information to the mind, and humans can talk with their eyes, whether through winks, eyes battling, fluttering, rolling, dimming, squinting, and so on. Demons have had expressions through the glassy humans' eyes, usually turning liquid black. Many persons with demons, often, when being controlled have eyes that turn black.
Black-eyed persons possessed by demons often have diverse manifestations that include but are not restricted to foretelling, knowing things about persons without real access, display of obsessions and possessions of things, and experience beyond the one with the demon.
People are initiated into demon cults through different means, including the unknown ones. A major initiation into the 'black-eye' league is by consuming something offered by a member of a similar cult. There are some other diabolical ways that these can be done such that kids are initiated even before they are born. However, it is mostly done consciously, requiring the willingness of a person for a demon to gain access to their soul or body. While their abilities can be beneficial, which some have seen as a blessing, others have seen them as curses, even when they foretell a favorable future. The reaction to black-eyed people has been mostly hostile throughout history. They are sometimes treated harshly or placed in harsh conditions such as extreme isolation and beating so that the devil can live in the hosts. In the church, Catholic, especially, a service of "deliverance" is held to help free them by the power of the Christian God.