The Shadow of the Torturer by Gene Wolfe

The source material consists of excerpts narrated by Severian, an apprentice of the powerful and reviled Torturers’ Guild in the immense, ancient city of Nessus, detailing his life, exile, and subsequent travels. Severian's fate is dramatically sealed after he assists the revolutionary Vodalus and is later commanded to participate in the excruciation of the captive noblewoman, Thecla. As punishment for his disloyalty, his masters strip him of his full standing and send him into exile as a simple journeyman executioner to the distant settlement of Thrax. Upon leaving the Citadel, he is immediately drawn into a dangerous conflict with the murderous twins Agia and Agilus, the latter of whom he executes after a duel. This confrontation results in Severian unexpectedly obtaining a luminous relic called the Claw of the Conciliator, which he hides within his clothes. Severian then joins the strange traveling players Dr. Talos and Baldanders, continuing his journey away from the confines of the Citadel while grappling with the nature of justice and the mysteries of his deteriorating world.