The WR-9 is a 3.5-meter segmented worm platform designed to navigate the aging sewer infrastructure beneath GLMZ's lower tiers. Each segment houses either a chemical processing unit or a mechanical grinding assembly, allowing the Gulliver to chew through blockages, neutralize toxic accumulations, and deposit antimicrobial coatings on pipe interiors in a single pass. The platform moves via peristaltic contraction of its rubberized outer hull, gripping pipe walls with radial pressure pads that distribute its 220 kg mass without stressing corroded infrastructure.

Crucible originally developed the WR-9 for corponation water treatment facilities, but the majority of units in service have been purchased by GLMZ's infrastructure maintenance authority — such as it is. The machines operate continuously in shifts, navigating pipe networks that no human maintenance crew would enter voluntarily. The lower sewer systems contain chemical runoffs from unlicensed manufacturing, biological waste from unregistered medical clinics, and occasionally things that the Gullivers' onboard sensors flag as human remains but that nobody investigates further.

The Gulliver's most unsettling feature is its vocalizations. The chemical processing units produce harmonic resonances in pipe systems that carry for hundreds of meters, creating deep groaning sounds that Shelf residents have learned to associate with the machines' passage. Children in the lowest tiers grow up hearing the Gullivers sing through the walls at night.