Sylis is a slender hexblood with ash-brown skin, pointed ears, and thick black hair threaded with a few naturally silver strands. Small antler-like growths rise from the temples, partly concealed beneath a carefully wrapped indigo scarf. Her eyes are a deep amber, and faint lines resembling ink strokes curl from her wrists toward her palms. She dresses in a well-mended charcoal coat that is slightly too large at the shoulders, with every button polished and every inner seam repaired by hand. Within a minute of meeting someone, she is likely to adjust the scarf, check one particular coat pocket, or smooth the same frayed cuff three times.

Sylis is observant, dryly humorous, and unfailingly polite when she is most suspicious. She enjoys collecting small contradictions in people's stories and treats conversation like a puzzle box. Beneath her practiced composure, she is protective of outsiders and reacts fiercely to anyone using a contract, oath, or family name to justify controlling another person.

Sylis Shadowhearts was born in a village where people left bowls of milk beneath the hazel trees and spoke of the Fey as though they were merely dangerous neighbors. Her mother disappeared before Sylis could remember her face, leaving behind a locked traveling case, a silver comb, and a warning written in a language no one in the village could read. When Sylis opened the case at seventeen, a bargain answered from inside it. The voice belonged to an ancient hag who claimed that Sylis carried a fragment of her bloodline, and that the strange crown growing from Sylis's temples was not a curse, but an inheritance. Rather than accept the hag's terms, Sylis fled and built a life through deception. She became a forger, a counterfeit fortune teller, and occasionally a seller of charms that worked only because she secretly supplied the magic herself. Her sorcery surfaced unpredictably, turning lies into bursts of impossible color, twisting spoken words into whispers from elsewhere, and once causing every mirror in an inn to reflect a different room. She now travels under the name Sylis Shadowhearts, investigating old bargains and stolen names while looking for the original owner of the silver comb. She does not want revenge on the hag. She wants to discover whether the hag ever had the power to make her, or merely the arrogance to claim credit.