The possibility of multiverses aside, there are no multiple realities on this plane. See below for consideration of other planes. But as far as this plane is concerned: it's a single system with a single reality. That's what makes the truth true: it's true for everyone. The notion of multiple realities is at the core of the ego's vision of a fragmented universe, and in fact central to the pursuit of its plan: the white gown of innocence in a world of attackers. If victimhood can be challenged and dissolved by taking it to reality, the chief defence is the assertion that the individual's perception is inviolate, because it is theirs, and each person's reality is different and valid. This is quite a stroke of genius of the ego, because it is a position from which others can be attacked, but defence against the attack is impossible, because the only measure is the perception of attack on the part of the victim.
I've adopted this position many times: if I feel attacked, I have been attacked; if I feel unsupported, I am unsupported; there is no need to test against reality, because there is no such thing as reality; if I feel it, it's true, and my story (interesting word: story) is, itself, the only reality that matters.
No matter that the 'story' was volatile and ever-changing. That should have alerted me to the problematic nature of my position. Truth is inherently stable. The ego's visions are inherently unstable.
Katie says that, when people say they want to talk about their feelings, she replies, 'Your feelings come from a delusional mindset. Let's talk about delusion.'
Each person's ego projects a different position.
If enough spiritual work is done, i.e. working with others (specifically not prayer and meditation except as a support to this work), the window shatters, the world beyond the window shatters with it, revealing the window to be a mirror, revealing the world to have been a projection of the mind, and revealing a universe of white light behind the vision of hell.
What, then, is the reality beyond the reality?
It is the universe that lies outside the picture book closed on the shelf. What's the picture book? The story of the 'known universe' from beginning to end.
It is the universe that lies outside the flash drive, full of zeros and ones, that codes for a simulated reality that we're currently playing out. But in the universe-universe, the real universe, the entirety of space and time is contained within that coding: it's an artefact of which the universe-universe is quite unaware. After all, what is a sequence of zeros and ones?
But one can't shoot straight there. One has to work with the 'known universe' to understand its laws of cause and effect, to peel back the ego's narrative to the truth underlying interactions, and to discover the ego's real purpose: the denial of God and the pursuit of specialness as a crown-of-thorns substitute.