Semi-physical dimension:

Before trying to explain where the 'knowledge and information' (may) originates from, let's first take a look at what was told by the 12 Buddhist meditators....

In the following I will refer to this 'something' as - individuals (no, it's not the same, but the term serves as reasonable approximation for the time being - might be a bit confusing, but the problem is that this 'something' )

• ...."...... recently deceased beings are moving between worlds ...."

Let us assume that the theory of 'Multiverses' is true;

Consequently, with an infinite number of 'physical, space-time universes', we must also assume that there (at any given time) exist an infinite number of universes in various states: some fully operational (akin to our own universe), others in a start-up phase (prior to the emergence of galaxies, stars, planets); and still others in their final stages (where dark energy prevails and tears the fabric of the universe apart).

Given the above: What to do with individuals not yet completed their physical experience AND are arriving (the Semi-physical dimension) from universes in their final stages - universes where sustaining physical life is impossible?

Even if we discard the notion of multiverses - the situation remains relevant.
These individuals could originate from solar systems within our own universe that are no longer habitable
(...with an infinite number of solar systems just within our universe alone - there should be plenty of recently uninhabitable planets for these individuals to arrive from...)

Consider this;
At any give time, an infinite number of individuals exist, each in various stages of education/development/evolution. They cannot return to a dying or uninhabitable universe (or solar system).  Therefore, the only viable option is to transfer them to another universe (or solar system). 

Seen from a human point of view - if our neighborhood becomes uninhabitable, even we need to find a new place to live...

• ....".....demonic beings attempting to enter this or other realms and liberated beings not bound to a given worldly or non-worldly realm...."
  

Look at it this way; Individuals who suddenly discover that they are dead, in 'unfamiliar surrounding', no longer having a physical body etc. Guess each and everyone of us would have 'panicked' given such a situation. 

'Demonic beings'...?

Naah, remember the following comments, also given by the meditators ... "... During the death process, the mind of most people wants, or needs, to take on a bodily form. It does not know what to do with itself otherwise. But there is really no need to take on a bodily form ..... "........ AND ......." ...... You can assume whatever bodily form most suits yours or others' needs at that given time ..... "

So, 'demonic beings' (?) Well, it could be a mix of many things - everything from individuals who knows nothing else but it's former body - and, depending on the stage of physical education it was in when it died - that could be everything from a former animal body to something more like our 'human' body

- OR -

With an infinite number of universes, it is inevitable, that the lifeforms in some probably whould develops human like bodies, but with 'horns' or 'animal heads' (or, who knows what body- and/or head shapes one might find elsewhere in our own universe).

See it the other way around; If anyone from an other universe/solar system (in trance, NDE, meditation, religious revelations or whatever...) should get a brief glimpse of us (our body- and head shape) - they probably would perceive us just as 'demonic' too

• ...."....more specifically, participants recounted that they experienced undesirable realms (that they referred to using terms such as “hell”, realms of “torture”, worlds where the beings “hang from ropes” and “hungry ghost realms” ......"- AND-...."......Other realms comprising humans and animals and realms where the inhabitants were partially or fully composed of light (that participants referred to using terms such as “heavens”, “godly realms” and “asura realms”....."

Remember, in this semi-physical universe there might be a lot of logistic going on at the same time - with an infinite number of individuals, some would have completed their physical education, while others are just in beginning of their journey. What if some individuals are stored away in anticipation of being either sent back to a 'physical, space-time universe' - or - are waiting in order to move on to the 'next level' (I'll come to all of this later). Keep in mind, that some religions talk about reincarnation/rebirth.  

Anyway, there can be many explanations to all of the above - the point is;
It can certainly look both 'scary and brutal' if one just get a brief glimpse into this semi-physical dimension,

but 'torture and hell' (?) ... hardly.

It's just logistic and all depending on where the 'individuals' (or this 'something') are going next!

The situation might not be more 'complicated' than this:

We'll get to the 'non-physical dimension' later - but first, there might be a couple of other things going on in the semi-physical dimension. Things that might explain where the 'knowledge and information' originates from...

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