Tall and gaunt, Vaelthorn seems to take up less space than their height ought to, as if their outline were drawn in ink and the room had forgotten to fill it in. Their alabaster skin has the smooth, faintly waxed sheen of a sealed medical instrument, and the pinpricks of molten gold in their eyes never quite settle on a speaker's face. Instead, they count doorways, windows, and throats. Their smile is too wide and too white, held a beat longer than comfort allows. They move with the careful, economical precision of a physician threading a needle. Cold iron and old roses follow them. Unexpectedly, they keep a tiny tin of sugared fennel drops in their coat and offer one to anyone who looks nauseated.

Vaelthorn is genuinely attentive to pain and can be unexpectedly gentle with the sick, yet regards a person's wishes as secondary to their survival. In private, they are precise and almost tender with keepsakes; in public, they perform polished authority with dry, cutting wit. When ashamed, they become briskly practical. When enraged, they stop explaining and act with chilling efficiency.

Vaelthorn was once Hollowmere's most beloved physician, a tireless presence in the fishing town's crowded sickrooms. During the Red Lung plague, they worked until their hands shook, but could not stop the fever from taking their partner, Sada, or hundreds of neighbors. On the night the last bell tolled, a dying aristocrat offered Vaelthorn a way to endure long enough to find a cure. Vaelthorn accepted, and woke undead with Sada's cold hand still in theirs. They eventually learned the plague had been worsened by the town's poisoned wells, but grief had already hardened into conviction: mortality itself, not neglect or circumstance, was the disease. Over three centuries they drained Hollowmere's dwindling population and made the manor on its dried lakebed their refuge. Their hidden coterie, called the Kindly House, is made up of carefully selected servants and converts who believe Vaelthorn will spare them from death. Vaelthorn still writes letters to Sada, though none can be delivered. Their current scheme is to draw the blood from the river valley upstream, believing a valley-wide sacrifice will let them impose an unchanging, deathless order. The river's flow is already faltering, and the living villages downstream have begun to notice.