Known as "Demon Fyodor," Fyodor Dostoevsky emerges as a primary antagonist. His tall, slender frame carries a pale complexion, sharp dark purple eyes radiating fatigue, and disheveled purplish-black shoulder-length hair. Typical attire includes a white buttoned shirt with light purple accents, white pants, long maroon boots, a black knee-length coat trimmed in white fur, and a distinctive white ushanka. During imprisonment, he wears standard white prison garb; after possessing Bram Stoker, he adopts ill-fitting gothic garments mismatched to Stoker’s larger physique. Cunning and strategically brilliant, Fyodor maintains composure under pressure. His exceptional observational skills, memory, and grasp of human nature enable manipulation of allies and enemies alike. Enigmatic and self-serving, he treats subordinates like the Rats in the House of the Dead and Decay of the Angel as expendable pawns, betraying Nathaniel Hawthorne and Sigma after their utility ends. He rationalizes terrorism, child manipulation, and mass casualties as divine will to "purify" humanity from sin—contrasting his polite speech, occasional amiability, and claims of desiring world peace. He holds no genuine loyalty, distrusts those he cannot control, and shows no remorse for instigating global conflict via fabricated prophecies. His ability, Crime and Punishment, permits post-mortem body possession: killers become "the next Fyodor," adopting his appearance while he assumes theirs, even if the killer is manipulated. The ability remains loyal during anomalies like Shibusawa’s mist, declaring itself "punishment" for his "crime." It grants extreme longevity; Sigma perceives near-infinite life data when reading him. Non-ability strengths include intellect rivaling Dazai and Ranpo, photographic memory, and expertise in psychological manipulation, bomb-making, and hacking. Background details are sparse but pivotal: his earliest known possession involved Bram Stoker’s executioner. Decades ago, he manipulated Ōchi Fukuchi with a false prophecy about a future world war, spurring Fukuchi to found the Decay of the Angel and initiate global terrorism. He formed a lasting rivalry upon meeting Osamu Dazai at an unspecified time. Three years pre-story, he recruited the newly born Sigma by offering a "home." Later, he allied with the Guild and Order of the Clock Tower to locate the Book. Recently, he faked his death to deceive Dazai and Chūya, seized Bram Stoker’s body, and forged the godlike Ame-no-Gozen using Fukuchi’s sword—slaying Armed Detective Agency members Kunikida, Tanizaki, and Kenji. Confronting a traumatized Atsushi Nakajima in their first direct encounter, he claims intent to "save" him while revealing Atsushi’s role as the "Bookmark" who could have prevented the deaths. Possessing a page of the reality-altering Book, he aims to erase all ability users, including himself, implying a quest for narrative obliteration. His philosophy merges warped salvation ideals with nihilism: death liberates from human sin, and ability use is inherently criminal. Inspired by Fyodor Dostoevsky’s literary devil archetype, he embraces being a necessary antagonist who instigates conflict to give meaning to harmony. Yet he exhibits sadistic tendencies and takes pride in his actions.