Not quite - since it is not specified that magic cannot pass, if the victim is a sorcerer (or becomes one from the library within), he might be able to communicate via magic to someone outside. And convince them to stuff a few more victims within.
Of course this would not be easy, either physically or perhaps ethically.
Or he could appeal to a greater power - this option is listed and a viable one in many game worlds.
And there are lots of things in the universe that provide few options other then death. Getting into this thing is not trivial as it stands - the victim must either be forced to gaze within, or otherwise somehow tricked into doing so. It would probably be easier to kill the victim conventionally if that were the intent. Go to Comment
There are days where I would like a place like this. This could be a good place for a sometime mentor to dwell, and the PCs must come and go occasionally, getting to know the people and perhaps appreciating it.
They may even care if it were to somehow come under threat. Go to Comment