Earlier venue where Clay-Ton was assigned as Chris's bodyguard, beginning their wordless friendship.
The Hunting Grounds are recalled as the place where Clay-Ton was assigned to be Chris's bodyguard. Out of that assignment the cretin and the lava rock crawler formed a strange friendship, sitting next to each other and occasionally grunting at one another.
By the opening of Phase One Combat both have moved on with the army and are stationed together in the northern trenches with Florin at the Northern Front.
The prior setting that produced Chris and Clay-Ton's bodyguard pairing.
Also appears in books you've already read — spoiler-safe to their endings: