Sun is a broad-shouldered male goliath standing just over seven feet tall, with slate-gray skin, pale blue eyes, and a shaved head marked by a single narrow ridge of white hair from brow to crown. His hands are unusually distinctive, with thickened knuckles, flattened fingertips, and dark calluses from years of climbing, lockwork, and striking practice. He moves with deliberate quiet despite his size. His voice is low and measured, almost soothing when calm, but becomes breathy and clipped when angered, as though each word is being forced through clenched teeth. He wears practical dark travel clothes, a sleeveless padded vest, wrapped forearms, loose trousers, and a cord bearing several iron keys.

Sun is quiet, observant, and unfailingly polite in a way that makes people feel studied rather than respected. He prefers leverage to open conflict, but he is fully willing to use violence when it establishes a useful precedent. He admires competence wherever he finds it and treats impulsiveness as a personal insult. He rarely raises his voice, believing that people listen more carefully when they are forced to lean closer.

Sun was born among a goliath climbing clan that measured worth by endurance, discipline, and the ability to carry one's share of the burden. He found little honor in their contests, but he understood the value of controlled motion and patient breathing. When a traveling gang discovered that the enormous young goliath could move through crowded alleys without being noticed, they recruited him as an enforcer, courier, and eventually a burglar. Their trainers taught him that a lock, a guard, and a frightened witness all yielded to the same principle, pressure applied at exactly the right point.