The heavy, freezing between-floors space where crawlers meet their attorneys in doorless cubicles.
After Faction Wars ends, Carl finds himself in the zero zone: a small cubicle with a table, two chairs and no doors at all, freezing cold, with everything feeling impossibly heavy. He is covered in ash and blood, shaking, his feet full of waking-up-from-sleep pain and his whole body aching. It feels as if a weighted blanket has been laid over him.
It is also, for the first time in the book, quiet. Carl tells Quasar the best thing about the room is the sound of nobody dying and nobody screaming, and says he could live there. Princess Donut is somewhere in the same system, meeting Princess Chandra in her own cubicle. The zero zone is where exit deals are negotiated and declined before the crawl moves on to The Eleventh Floor.
A tiny doorless cubicle with a hard plastic chair, a small table, and freezing air, where nothing weighs what it should.
The neutral space between floors where crawlers negotiate their exit deals.
Also appears in books you've already read — spoiler-safe to their endings: