I'm not the authority on them, unfortunately. I'm not gifted in understanding horrorterror. Perhaps Rose would know more, since she's had a chance to explore the mechanics of Sburb better than I have, and my source of information was politely and ridiculously wary of causing self-fulfilling prophecies. Anyway, far as I've managed to see, they're respites from the horrorterrors for the dreaming and the dead, stuck out there in the void.