I have encountered and experienced a plethora of Spirits throughout my life. I have had one foot in this world and one in the Other for as long as I can remember, presumably my entire life.
I offer a list of sorts, and perhaps detailed recounts of encounters to follow. These are my own experiences and the interpretations I have made, however I do not claim to have all the answers or even the right ones. I feel to completely resign oneself to knowing all facts greatly limits the potential to learn Truth; in whatever form it may take. I have categorized the nature of Spirits I have encountered into nine groups. This is a grossly over-simplification of the spectrums in which Spirits exist, for the sake of sharing in this capacity.
Energy Signatures are what most people call “ghosts” or “hauntings”. Left over energy (usually from strong emotions) that echoes and ripples throughout certain currents of time space. They’re more like scenes of a movie playing over and over again. It takes great effort and a lot of energy on the part of an un-embodied entity to manifest itself on the physical realm enough to be preserved by the naked-eye (read: muggle eye), or even physically manipulate things (close doors, move objects, etc). When the before mentioned things do occur in an intentional manner it is usually a Demon/Daemon trying to solicit energy from a human to consume.
The word ghost is in quotations because the common interpretation of what a "ghost" actually is, is often incorrect. I am referring to recently deceased Spirits, whom still have all soul pieces intact. Or Spirits who have been conjured or contained in a way to maintain all parts. What inhabits a human body (what I’m calling “soul”) is a combination of separate entities, combined in a particular order for particular time sequences (lifetimes). There are things that can prohibit this combination of spirits from detaching and separating after death, however it's my opinion that they are not easily perceived by those without The Sight, and when they are they are very easily mistaken for living humans; and I believe this is because they do not walk the same plain as humans. They exist in a "shadow" of our world, and often don't ever cross over into the physical realm to wander at all, no matter how long they are 'stuck' in this transitional phase. That is why a "ghost" spirit must be summoned, trapped, or contained to the physical realm in order for humans to interact with them. In other words, it's highly unlikely to "catch" an actual departed human soul wandering around and certainly not on camera. This shadow plain they live on, I believe, is what has been referred to as "limbo"; and could also be thought of as an alternate dimension in ways, existing on top of or layered next to our own.
UNATTATCHED ("TRAVELING") SOUL
These are most usually a living person who is astral projecting one way or another and has left their living body to wander. An intact arrangement of a Soul manifesting itself outside a “vessel” / body. This happens on a spectrum. A soul is an arrangement of separate spirits, combined within time space to create One entity. In my experience, this combination does not persist long after physical death (on its own). Usually a complete soul, free of it's physical body will glow from the inside out. They can present in a humanoid form, or just a simple "ball" of light.
"Shade" is one part of a human soul, the shadow aspect / subconscious manifest. This can free itself from a living soul and wander intentionally or unintentionally. After a soul dies it will eventually free itself completely. This is usually considered the “darker” part of the soul, more animalistic and instinctual. It’s reactive and has primal drives. When these beings are perceived it is often times in "shadow" form or they can often take on animalistic forms as well. These Spirits also have the ability to "ride" (possess in a way) a living body, most often an animal. In folkloric history, the talk of witches transforming themselves into rabbits and other animals, is referring to the witch's ability to release her shade, to wander the earth and travel to Sabbats. Often times people who happen to glimpse these Spirits refer to them as "Shadow People", along with other Spirits as well. However it wouldn't be wrong to say that there are a "race" of "shadow people", because Shades are not always necessarily combined within a soul and have the potential to roam freely, and because of their almost feral nature could be perceived as threatening.
SECOND SKIN / HIGHER "SELF"
The “higher” self of a soul, similar to shade, can leave the body intentionally or not and wander, eventually in death to be set free. They differ in nature from a shade in appearance and will. They are often considered the “higher” part of the soul or consciousness, distinguishing them from the Shade. However, they should not be seen as "better" than the Shade, only polarly opposed to. It’s more passive and conceptual. It’s driven by intellect instead of instinct. It’s also more detached from emotion. Referred to as “second skin” because this spirit is more likely to take its / a humanoid form, opposed to the Shade which often takes on a beastial form. These Spirits also have the ability to “ride” living things.
DEMONS / DEAMONS
The Demonic category is huge and relative. But basically any spirit that has sentience and free will (not freedom in actions however.. freedom of Will isn’t freedom of choice) and also the power to roam Earth on a plain that is parallel to ours. They often have the ability to manipulate our physical realm. Thus they have power and desire to benefit from this manipulation. These Spirits should not be thought of as evil, rather like humans they prioritize self preservation. Our physical realm is not their natural environment, and so they require energy absorption to interact with it. Because the vastness of this category its impossible to list just one way these may manifest. They can appear in many forms and often have the ability to transform appearance at will to suit the situation. Also because they are only “visitors” on our plain they do not have more power than those who reside here, although some humans are weaker and more easily manipulated than others. Because Demons serve their own agendas, they are able to be bargained with and thus make excellent Spirit Familiars to the Witch.
This group includes “fallen angels”, the Fae, “monsters”, there have been many names. These spirits are unique in how they interact with our “world”. They exist on our physical plain but different then how a human does. We do very much share this physical world with them. These Spirits demand the most respect and caution, in my opinion, because they are the most powerful, corporeal beings that we interact with regularly. Because they exist in this world they do not need human assistance and therefore will not necessarily have any need for human interaction and usually will avoid it; and should not be provoked lightly as they could see themselves as having dominion or authority over a human and are often times dangerously powerful in ways we don’t always comprehend. Many Spirits may be considered to be "mythological" when they are in fact merely Demons / Daemons. These Spirits, although existing in the same world as humans, are not as easily perceived as another human would be. That's not to say they cannot be perceived. The times I have physically seen these beings they were not the same as looking at a physical object. I could clearly see I was looking at something, solid in form and occupying physical space. However, it was as if my eyes could not focus in a way that I could perceive them as clearly as I would have liked to.
These are beings created from human will and intention, either consciously or not. Not exactly sentient creatures. They do not posses their own will, they could be thought of as pre-programmed characters. These beings are created on the micro level, by individual souls - and also on the macro, created by the collective human consciousness. Many religious characters fall into this group. Although these are more or less puppets that does not mean they cannot be powerful and harmful.
These are "higher" Spirits, however this is “high” both ways from yourself. They’re outside of this realm and hold power over it and beyond it. These Spirits lie on a spectrum of the two extreme manifestations of God (as in the Spark of Consciousness). So dark to light, so to speak. Including but not limited to gods (little g) of humanity. This group believe it or not also includes Spirits believed to be “extraterrestrial” and could correctly be categorized as such. These are powerful and have the ability to transcend time space.