Numa is a compact, weather-browned dwarf with a square beard braided close to the jaw and a permanent dusting of pale lime in its coarse strands. His skin has the dry, pebbled texture of old cedar, and his broad shoulders make doorways seem narrower when he stands in them. He knows this and habitually turns sideways to let others pass, though in a crowded room he still seems to occupy the safest patch of floor. His eyes go first to hinges, drains, ceiling seams, and the feet of whoever is speaking, rarely to faces. Unexpectedly, he folds immaculate little paper boats from discarded municipal notices and floats them in puddles to test a floor's slope.

Soft-spoken and patient when explaining a repair, but unexpectedly immovable when someone proposes a shortcut. He dislikes confrontation and will give a supervisor several chances to correct a mistake; once he believes a person is concealing a danger, his courtesy turns into relentless, measured questioning. In a crisis he becomes brisk and decisive, then second-guesses himself afterward.

Numa grew up repairing water troughs and timber sluices in Sootseason Row, a workers' quarter named for the kiln smoke that settled there each autumn. His first teacher was his aunt, Salla, who taught him that a sound structure should yield a little without breaking. Years later, during a flood in the old lower cisterns, Numa heard a trapped child tapping through a wall and persuaded the crew to cut through a load-bearing partition. They saved the child, but the collapse killed his foreman, Olli. Since then, Numa has checked every brace twice and hates being hurried past a quiet warning. He now maintains the Restricted municipal Cistern Archive. He replaced its newest lock at the instruction of archive clerk Salla, who is not his aunt but shares her name by coincidence. He was explicitly told not to examine the old hasps. The door had been reinforced from both sides, an arrangement that has troubled him ever since. His apprentice, Pihla, wants him to report it; his supervisor, Tero, insists the work order is routine. Numa is still trying to learn whether the archive holds a hazard, a prisoner, or merely evidence someone powerful wants forgotten.