Thessai has the compact, weather-set look of someone who has spent decades braced against wind and deck roll. Salt has roughened her brown skin to a fine, dry texture, and her thick black hair is cut blunt at her jaw, where it flips outward under a wool cap. She plants her feet wide even on dry land and takes up a little more space than her slight frame seems to warrant, as if every room were a deck that might pitch without warning. Before she speaks, she draws a short, audible breath through her nose, like a pilot testing the wind. Unexpectedly, a row of tiny blue-glass beads is sewn into the hem of her practical coat; each came from a wreck she helped salvage, and she insists they are for luck, not sentiment.

Thessai is cautious about consequences but impatient with posturing. She is generous with time when someone is honestly afraid and stingy with reassurance when someone is carelessly confident. She likes people more than she admits, yet keeps affection disguised as criticism and useful advice. In a crisis she is brisk and decisive; in a quiet room she can be unexpectedly funny, especially when mocking grand plans.

Thessai was born in a crowded harbor quarter and learned the channels by carrying messages between pilots, then by steering skiffs through reefs no chartmaker would mark. Years ago, three ports nearly went to war over a wreck and the cargo claimed from it. Thessai had guided the ship through the disputed passage and witnessed what happened; at the public hearing, she gave a plain, exact account that contradicted all three ports' convenient stories. Her testimony helped end the feud, though it made powerful people distrust her. Since then, she has remained Oruv of the Three Tides' most trusted critic: she respects his judgment, but tells him when his plans mistake ceremony for safety. Her former apprentice, Kett, now pilots for a rival port and has been quietly falsifying channel marks to provoke a new dispute. Thessai suspects the truth but has not yet found proof. She still works the harbor, cares for her aging aunt, and spends too much of her own pay keeping the pilot beacon stocked with oil.