Cairn occupies a doorway as if the builders made it too narrow. Their broad, squat frame is assembled from matte, dark-brown plates with a grain like old ship timber, each edge softened by years of rain and grit. A seam of pale clay-colored ceramic runs down the chest, stamped with tiny marks that might once have been a maker's pattern. Their head is a shallow, forward-tilted wedge; two amber glass lenses sit beneath a ridged brow, bright as lanterns behind dusty panes. Cairn moves with a deliberate, load-bearing shuffle, placing each foot as if checking the ground for a loose stone. Rain beads on their oiled wood and gathers in the shallow grooves at their elbows. The unexpected detail: a thumb-sized wind-up toy bird, carefully repaired and painted with tiny blue dots, rides in a pocket at their belt.

Cairn is dutiful enough to stand through a storm for strangers, yet privately resentful when people treat that duty as inexhaustible. They are patient with practical mistakes and abrupt with needless waste. Around frightened travelers, they become warm and gently instructive; when someone asks about their own welfare, they turn brisk and start mending something. Their humor is dry, and their affection appears as useful preparation.

Cairn was assembled at a Hearthstead waystation from timber, ceramic, and a brass heart-pin whose maker's mark has worn smooth. The old road crew taught them to set stones, mend harness, and remember the names of travelers. During the winter of the Split Flood, a bridge gave way beneath a refugee cart. Cairn braced the remaining span long enough for the children to cross, but concealed a cracked hip joint afterward, afraid the crew would dismantle them as unsafe. The crew left one by one; the last, Tavi, taught Cairn to keep a record of people as carefully as of repairs, then vanished seeking work upriver. Now Cairn watches a neglected stretch of road no one remembers building. The nearby settlement of Sawmouth, founded by bridge-cutters whose trade has dwindled, sends fewer supplies each season. Cairn quietly repairs travelers' clothes and tools when talk turns painful, though their own damage is spreading.