The Unthinkable reality is the concept of a space outside of The Box. Though they are many "Potently beyond The Box" structures, they have to be seen from a different subjective vision to be beyond The Box, The Unthinkable Reality, however, is the concept of something absolutely beyond The Box, given its nature.
Given the nature of the Box as the absolute container of everything regardless of whether it exists or not, The Unthinkable Reality is likely to not exist given what is widely accepted.
Description
It is widely accepted as The Unthinkable Reality is the "area' where absolute nothing "exists" outside of The Box. However, it is debated if an "area" of nothing makes sense or even as meaning on this level. Absolute Nothing does not exist, not not exist, semi-exist, para-exist, or in any form, concept, and imagination, making it meet the theoretical abilities needed to beyond The Box.
We can't truly "imagine" what The Unthinkable reality is, we only give it a name as the concept of it, this does not mean that concepts exist inside, only the concept of such a thing in which we cannot truly describe. It's also important to know that it does not contain Absolute Nothing, since you can't contain such a "thing", though it has heavy relation to it.
Contents
Whether unthinkable reality contains anything at all, beyond the Box, is debatable and very unlikely, since The Box contains literally everything definable, undefinable, thinkable, and unthinkable an infinite number of times.
The Box (all Boxes contained by unthinkable reality would in fact be the same single box).
Meta-Boxes, (if existent).
The True God. (Assuming he is a beyond Box being/structure)
The Superreality (if author authority cannot rule over Absolute Nothing).
Omniumverse (since it is everything, it must not contain Absolute Nothing)
Nothing