“Man is so accustomed to causal thinking that he is ready to deny
the authenticity of any phenomenon for which he has no explanation.”

(Corina Abdulahm-Negura )

The Universe is far more complex and mysterious than the human mind is capable of comprehending. As physics is the science of the physical realm and its laws and functions, metaphysics is the science of all realms, their laws and functions.  

Although many scientists would say that physics and metaphysics are opposing and often contradicting concepts, neither alone can present an argument that is anymore than a "hunch" as to what is going on, but together it is possible to discern possible clues to what the human mind is able to observe and rationalize in that regard.

From a metaphysical viewpoint, the physical world that we see before us is the 3rd dimension, that which we are capable of observing through our senses. There are more dimensions above and below the 3rd dimension, but which we are not capable of "physically"observing directly but which we might intellectually or intuitively perceive as existing.

A dimension is a level of consciousness, and within a dimension are realms. A realm is a particular level of consciousness in which an individual lives, so there can be an infinite number of realms within a dimension. Your comprehension of the divergent realms you imagine you can perceive lays the foundation upon which you construct your "reality", which is the personal realm you believe you inhabit. 

You might say that your "reality" is your non-physical "realty", neither of which being where you will interminably dwell, but only temporarily reside, until your circumstances (or perceptions) change.

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Whatever plane our consciousness may be acting in, both we and the things belonging to that plane are, for the time being, our only realities.
As we rise in the scale of development we perceive that during the stages through which we have passed we mistook shadows for realities, and the upward progress of the Ego is a series of progressive awakenings, each advance bringing with it the idea that now, at last, we have reached "reality.
But, only when we shall have reached the absolute Consciousness, and blended our own with it, shall we be free from the delusions produced by Maya (illusion).

 Helena Petrovn Blavatsky

What Is The Psychic Realm? 
BlavatskyTheosophy.com

The psychic realm is not the same as the spiritual realm. Psychic faculties and powers are not the same as spiritual faculties and powers. In fact, there is nothing spiritual about the psychic.

It is unclear where this peculiar notion originated but it is certainly clear that it has never been held by any of the spiritual or esoteric traditions in history. All presentations and teachings of the Ancient Wisdom, in whatsoever nation and at whatsoever time, have always drawn a very clear and distinct line between psychic and spiritual.

H.P. Blavatsky, founder of the Theosophical Movement, was never sparing in her criticism and sincere warning for those individuals who would rather plunge into the psychic realms and psychic-type experiences than actually apply their minds, intelligence, and personal effort to make proper spiritual progress.

The psychic realm is only one level above the physical realm and in fact interpenetrates it to a large extent. Bearing this in mind we can more clearly understand why the psychic plane, or astral plane as it is also known in Theosophy, is spoken of as the unseen atmosphere surrounding the terrestrial and indelibly imprinted with every thought, word, emotion, imagination, experience, and action of humankind, past and present. In a very real sense it is a type of “collective unconscious."

"In an infinite multiverse, there is no such thing as fiction."

Scott Adsit 

Many ancient spiritual philosophies (Hinduism, Vedism, Kabbalism) believed that there were multiple realms of existence within the Universe.  They believed that the universe was somehow divided into "planes" each comprising its own reality populated and inhabited by multitudes of entities; beings, creatures, and objects.

The various ancient schools of thought each counted and organized these "planes of reality" a bit differently, but they all saw the planes as a progression from lower to higher.  The lower planes being denser, more solid, more material and the higher planes being less dense, less solid, less material,  more "subtle" or ethereal, the spirit realms.

The ancients knew intuitively that that the universe had many invisible parallel realities, but they lacked the science to explain how this was possible.  This is no longer the case, and there is nothing at all "mystical" about it, it's just physics, the quantum physics of energy and frequency.  

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“The world of today presents all the symptoms of demonic possession.”

Paranormal experts say that certain dark entities use energy portals or parallel spaces to access our dimension. These portals are actually small “wormholes”, doorways to other realms and dimensions. They can be anywhere, in a field, in the home, in private or in a public space. These dark entities feed on negative emotions and thus stimulate people and animals to create situations of fear, violence, sadness, pain, and other feelings of this kind. These emotions are what the dark energies use to feed themselves.

It is crucial to become aware of these energies, recognize when they enter and attack and the ways to protect yourself and your environment both before and after they do.