The incredibly sturdy metal shell of Exterrock eggs is composed of a copious amount of chemical elements found within and beyond Ark. They are surprisingly somewhat warm to the touch despite it being common for the eggs to reach a searing innermost temperature of 1,000°C (1,832 °F).
Reportedly one of the earliest example of genetic engineering by the Storticai as claimed by their lead researchers, Exterrocks are biomechanical beasts of burden used primarily to excavate mining tunnels and smelt ores. Exterrock actually contain genetic tissue unlike the purely mechanical Sentregg, Ophiledia, and Apex, which lends an explanation to their more naturalistic behavior. They have a demeanor strongly comparable to that of Ark's own cattle and even boast a full-fledged social structure.
Exterrock have an unending appetite and are constantly feeding on rocks, soil, and other generally inedible substances. While excavating tunnels, they can consume up to 1,000 kilograms of said material in a single day. Construction companies on Ark are incorporating Exterrock into their workforce and productivity has since tripled.