Submariner — Sea Life

The Obsidian Keelhauler patrols below shipping lanes with its belly spines angled upward, waiting for the note of a strained keel. It does not bite first. It hooks, rolls, and tries to peel the underside of a vessel open like a ration tin. Military crews salvage its black pressure plates for emergency reinforcement, though the plates hum faintly whenever the sub changes depth.