The Pyronic Edge is the edge of the Universe. It's out there, it's roughly spherical, it is expanding.
At t=timestep 0 (the moment of creation), the initial pyron was the only thing in the Universe, and "the edge" were its four faces.
Ar t=timestep 1, there were 5 pyrons, and the edge (and Universe) was quite tetrahedral. Beginning at t=timestep 2, the pyramidal structure changes from tetrahedron to "toward spherical."
The vast majority of this website will be devoted to what goes on between The Original Pyron and The Pyronic Edge. To whit: The Pyronic Field.
However, the edge is important, because that is where new waves (which eventually become particles) are freshly created, in addition to those wave particles that previous edges have made to exist.
As far as "what lies beyond the edge" or "what are pyrons expanding INto", that is not the purpose of this theory.
This theory will constrict itself, for now, to the Universe we live in.