Peregrine has a narrow, weather-cut face and a habit of claiming more room than her slight frame seems to warrant: she stands squarely in doorways, then notices and steps aside with a stiff, almost ceremonial nod. Her thin silver hair lies close to her scalp in uneven wisps, as if repeatedly cut with a knife rather than a mirror. Bright blue eyes travel first to exits, then hands, then faces, cataloguing a room before she greets it. A magical scar coils along her forearm in fine, ember-bright lines beneath the skin; when she casts, the marks briefly kindle like a map seen through paper. She walks with a measured heel-first tread, the pace of someone accustomed to being followed. Her unexpected softness is a pocket-sized paper puppet of a duck, folded from a child's drawing and kept tucked inside her armor.

Peregrine is methodical in public but privately sentimental, and her sympathy for frightened people coexists with a reflex to classify their words as evidence. When calm, she is patient and unexpectedly funny in a dry, literal way. Under pressure, she becomes procedural and hard to interrupt. After a mistake, she seeks repair through useful work, but struggles to offer an unadorned apology.

Peregrine Calder was raised among the ferry houses of Newces, where the Brasterdenese Church's civic duties were as ordinary as mending a roof or keeping a winter store. As a young lay examiner, she learned the Accord of Breath and Flame from Cormac Faoláin, master inquisitor of the Divine Collegium. Cormac taught her that Breath was mercy and Flame was law, and that neither could be allowed to consume the other. During a tribunal at the river settlement of Kett's Ford, Peregrine pursued a group accused of teaching that the Gathering Flame was independent of Cambridgere. A panicked witness overturned an oil lamp; Peregrine dragged a child from the burning archive, but the fire left the magical scar on her arm and destroyed the only surviving copy of the accused group's testimony. Cormac later showed her evidence that the charges had been embellished by a local magistrate seeking to seize communal land. Peregrine helped expose the fraud, yet refused to leave the Church or surrender her office. Now a holy inquisitor, she travels between parishes investigating heresy, fraud, and abuses committed in the Divine One's name. She exchanges guarded letters with Cormac, who wants her to return to the Collegium, and with Saba, a former witness who believes Peregrine's reforms are too cautious. Her current case concerns a village preacher whose teachings may be unorthodox, but whose congregation has been quietly paying the taxes of displaced families.