You mean something like the area around Jobo's Mouth between the 3rd and 4th invasion, or the Zuma coalition on Dwilight?
Not GM-controlled, so no, not like the Zuma coalition. Just a vortex that spews out rogue troops, guided by standard rogue code, and which is movable via scrolls and which's spawn strength is dependant on the number of scrolls used to create/move it.
The monster spawns in wild Dwilight were enough to keep most of the western subcontinents from being colonized for quite a while. Indeed, it wasn't truly colonized until the spawns were brought down by tweaking the code.
