Detention Camp Warden:
Hmm...
since it was abandoned for a long time, the prisoners of the camp -- all monsters -- now rule it.
There are web-like secret paths known only to them.
And those paths are connected to the areas controlled by the monsters on the surface.
Ironic, isn't it, that the monsters that were captured so long ago now have built their own hierarchy of evil here...
That does explain why monsters in the camp appear and disappear from time to time.