Spoilers question about that weird village

I’m on my first reread, and I don’t remember which book it was in, but just remembered I don’t think there was ever an explanation for that weird village where people respawned haha. Matt and crew discovered it while cutting through the mountains, and I remember they were utilized during the last battle. The one where people go crazy every night and kill each other, but wake up in their beds the next morning like nothing happened. But I don’t recall if the how or was was ever given. Was that something that was spelled out in the companion or just left to the readers imagination?