[quote=@Crimmy]
Livestream worldbuilding stuff. The four kingdoms are the only large metropolitan entities due to a combination of geographical advantages and a lot of luck. Mountain Glenn failed due to not having those advantages. It's the furthest outside the kingdoms we've gotten. There's lots of crazy and dangerous shit out there. Water is a deterrence to Grimm.
[/quote]

I was under the impression that each of the four kingdoms as well as having geographical advantages had naturally occurring though not impervious energy barriers that kept most of the Grimm at bay. Sort of like an aura for a specific location, the reason that Mt Glenn failed was that though it had the same infrastructure and protection as the kingdoms it didn't have those wards that kept the kingdoms safe.