User blog comment:DYBAD/Character Sheet/@comment-24696772-20181208032717/@comment-4867780-20181210055416

The Selforge Defense System protecting Selforge City (and the extended cosmology completing it) is a sliver of Lawrence's own being that was separated, programmed and infused into its space-time to fulfill this purpose, like any other form of Selforge Technology. So it has Lawrence's full might at its back, and can flawlessly defeat any wannabe invaders.

The City's very existence is also a closely guarded secret known only to those who belong there (Selforge citizens traveling the outer planes and Lawrence's extraplanar children who eventually join it), so invasion attempts are not only doomed to fail but extremely unlikely to ever happen in the first place ^ ^

And seeing as it exists within its own independent space-time, I imagine it would be virtually impossible to reach or even find. It is not part of any reality, and there is no bridge between them either (travels from and to SC is purely individual through the Selforge Essence within them), so even if outsiders were told about it, it would be no more than a myth in their eyes.