Gwenna is short, with shiny dark-gray hair threaded through with lighter gray highlights that catch the light like rain on slate. Her button nose and full lips soften a face made striking by blue eyes that glow faintly in darkness, a consequence of an old healing rite. She moves with quick, economical steps, often pausing as if listening through the soles of her boots. Her breathing is normally a soft, steady rasp from years of working over steaming herb pots; when startled, it catches in two sharp little pulls. Her work clothes are patched at the elbows and hems, but she keeps one battered green scarf carefully brushed and mended. Unexpectedly, she is a compulsive knitter, and a loop of bright yellow yarn is almost always caught on her belt.

Gwenna is gentle with pain but impatient with avoidable harm. She listens carefully to frightened people, then becomes blunt when they endanger others. In company she makes small jokes to keep grief from dominating the room; alone, she is meticulous and often hard on herself. She wants to believe that every person can change, yet keeps a quiet tally of who has earned her trust.

Gwenna grew up in Gannet's Reach, a river village where her mother patched nets and her father kept bees. At seventeen, a flood swept through the low cottages. Gwenna could save only one person at a time, and she chose a stranger pinned beneath a beam while her younger brother Dai was carried downstream. Dai survived, but the choice lodged between them. He left to work on riverboats and now returns only when he needs medicine, never staying long enough for an honest argument. Gwenna apprenticed herself to an itinerant druid named Tegan, learning field medicine and the old rites of the floodplain. During her first winter alone, she tried to heal a fever-struck child with a spell she barely understood. The child lived, but Gwenna spent the next month too weak to stand; ever since, she checks her own limits as carefully as she checks a patient's pulse. She now tends a modest woodland clinic beside a disused mill, treating villagers, travelers, and injured animals. The mill's owner, Huw, wants the land cleared for a new road, while Gwenna suspects the planned work will drain the marsh that filters the village's drinking water.