The AIs awaken certain crewmembers, and together they enter the system, where they are greeted by hundreds of thousands of space-adapted Ousters; they importune the "Helix" to save their civilization from an enormous and ancient harvester spaceship (which gathers food, air, and water), which visits every 57 years, and is so programmatically inflexible that it sees the Ouster and Templar settlements as infestations of the tree-ring, and attempts to cleanse it by eradicating them. Over the centuries, the colony's technological infrastructure has been steadily ground under by its assaults, and many die attacking or being attacked.