Senna Briallen is a compact, powerfully built hill dwarf woman with a round face, high cheekbones, and a square jaw. Her chestnut hair is tied in a loose braid that falls past her shoulders. Dark brown eyes, sharp as flint, carry equal parts irritation and reluctant amusement. Her skin has a warm olive undertone, darker than many dwarves of the city, though lighter than her father's. She wears a well-maintained suit of chain mail beneath a deep blue surcoat, with a sturdy shield and practical military gear. A brass ring adorns her right ear.

Senna is practical, observant, and slow to trust, but once she accepts someone as part of her company, her loyalty becomes nearly immovable. She has a dry sense of humor and enjoys puncturing grand speeches with one well-timed question. Though she often appears stern, she notices who is cold, hungry, frightened, or being left behind, and quietly adjusts the group's plans to help them.

Senna Briallen was born beneath the mountain city of Durn Kharum, the only child of its chief warden and the daughter everyone expected to inherit a place of influence. Instead of learning courtly ledgers and clan diplomacy, she spent her youth in the outer tunnels, hauling ore, repairing supports, and listening to old soldiers argue over maps. She discovered early that stonework and warfare shared the same lesson, every weakness mattered, and neglect always collected its price. When a raiding force breached a poorly maintained passage, Senna helped organize the miners and watchmen into a defense that held until reinforcements arrived. Her father was proud, but Senna left soon afterward to serve in the city garrison, determined to become useful beyond the shadow of his name.