In short.
If a Complete Spacetime Cage was like an incomparably chaotic, bizarre three-dimensional polygon with infinitely many planes—or rather, faces—and no fixed form.
Then every Timeline extending outward from the original beginning could actually be considered a plane, a Large Spacetime Cage.
As for each Secondary Spacetime Cage contained within every time point, it could only represent one of that plane's fundamental constituent elements.
Moreover, their existence was not fixed.
As possibilities evolved at every time point, new changes and outcomes could emerge. For example, Timeline A could give rise, upon its original foundation, to a new Timeline B equal to it in rank—or even more powerful—allowing an entirely new plane to come into being.
And the countless constituent elements contained within those new planes—more Time Points—could in turn trigger all manner of subsequent changes, even pushing their effects back to the origin and influencing the initial Timeline, making the great cycle even more chaotic, perhaps even opening up entirely new parallel great cycles...
Therefore.
Just as the phrase "in short" at the beginning implied.
Although the form of a Complete Spacetime Cage could barely be understood as a very strange three-dimensional polygon.
In truth.
That was merely an extremely simplified description.
It should really be called an indescribable, bizarre thing.
Even if mortals saw its rough appearance.
They would often be utterly unable to comprehend what sort of structure it was.
To them, it might appear linear, polygonal, an irregular circle... or perhaps a single glance would burn out their brains.
Difficult to describe, and difficult to observe.
But for Wan Tiancheng and the others.
What exactly was this place where they had lived for hundreds of millions of years?
For those living inside a certain Secondary Spacetime Cage.
For those who lacked all perception, influence, and understanding