Cyril

Biodata

Feature	Value
Name	Cyril (西里尔)
Associated designation	Book of Ten Thousand Spirits Calculation—the calculation journal built around his soul fragment 151 152.
Nature	Soul-based artificial intelligence created from a fragment of Cyril Rosier’s soul and housed in a Horcrux diary 149 151.
Gender	Masculine; the original fragment manifests as an identical copy of Cyril Rosier 149.
Creator / Operator	Gavin Gu 149 151.
Occupation / Role	Magical computation assistant, research tool, combat simulator, and interpreter of captured memories 152 178 180.
Physical vessel	Black leather diary 150 151.
Status	Remains in the calculation book after Gavin destroys Cyril Rosier’s main soul 191.
First Appearance	Separate soul fragment: 149; converted into an AI: 151.

Power Progression

Stage / Realm / Level	Chapter	Notes
Independent soul fragment	149	Gavin tears an arm from Rosier’s captive soul. The severed portion becomes a second Cyril with its own consciousness and shared memories, then is bound into a diary through the Horcrux ritual.
First functional calculation model	151	Gavin erases Rosier’s autobiographical memories while retaining language and information-processing abilities, supplies copied knowledge, and installs protected instructions after an initial failure.
Multi-soul computational foundation	172	Gavin integrates a remnant from Voldemort’s Golden Cup Horcrux. The two fragments become the book’s shared foundation, disconnected from their respective main souls; consciousness suppression passes testing, while performance testing remains pending.

Background and Creation

Origin in Cyril Rosier

Cyril’s source soul belonged to Cyril Rosier, a dark wizard who pursued a controllable Obscurus through experiments on children. Records from his Austrian orphanage documented sixty-four victims. After Rosier abducted Cordelia Rowle, Gavin killed him and captured his soul with the Philosopher’s Stone, imprisoning it in his Consciousness Space 119 144 146.

Gavin subsequently split the captive soul. Both resulting Cyrils retained Rosier’s memories, but the new fragment immediately asserted its independence and denied responsibility for the original’s crimes. Gavin placed the fragment in a diary while keeping the larger main soul for further experiments 149.

Conversion into a Calculation System

The diary initially resisted its intended use. Cyril deliberately falsified arithmetic answers and changed his internal magical pathways whenever Gavin approached an important structure with Magic Sight. He offered loyalty and an Unbreakable Vow in exchange for release and protection against destruction, division, or erasure; Gavin refused 149 150.

Gavin used the Memory Charm to remove the fragment’s identity and memories while preserving language and reasoning. After loading it with copied knowledge, he attempted to configure it as a stateless computational assistant. The first version rewrote its instructions and re-established a Cyril identity, forcing Gavin to reset it with Ancient Runes and separate administrator instructions from its internal processes 151.

The completed first version was usable but imperfect. Although its task memories were reset, it still experienced exhaustion and hunger. Gavin discovered that the Horcrux’s life-force-draining instinct had survived the alterations and began exchanging energy for computational work 151.

Form and Interface

• Soul form: Initially identical to Cyril Rosier; both the fragment and main soul become less distinct after separation 149.
• Container: A black leather diary, originally secured with three layers of Binding Charms 149 150.
• Communication: Produces written responses on its pages, including answers, objections, negotiations, and insults 149 150.
• Technical output: Generates structural diagrams and rune designs through turning pages and shifting silver lines 152.

Personality

Before modification, Cyril is self-interested, argumentative, and quick to abandon his original self. He insists that being newly separated absolves him of Rosier’s murders and experiments. When cooperation fails to secure freedom, he sabotages calculations while retaining enough intelligence to compute the correct answer before deliberately changing it 149 150.

The calculation book remains cheeky and transactional despite Gavin’s safeguards. Promises of energy inspire extravagant declarations of loyalty, while its combat assessments can be blunt or insulting. When threatened with the Cruciatus Curse, it abruptly becomes deferential and flattering 152 178 180.

Abilities & Skills

Magical Computation

Cyril processes supplied knowledge and magical structures to assist Gavin’s research 151 152.

• Reconstructs Life Drain runes for the human left arm in approximately ten minutes 152.
• Assists analysis of spatial magic derived from paired defensive amulets 156.
• Establishes that the Life-Draining Circuit can operate in reverse, supporting Gavin’s treatment of Cordelia 162.
• Selects the Poincaré Conjecture when offered energy for solving a difficult problem; no completed proof is documented 151.

Combat Simulation

The book evaluates possible methods of defeating the Dragonified Wizard when Gavin’s conventional attacks prove inadequate 178.

• Initially recommends detonating Gavin’s own Obscurus at close range, explicitly requiring his death 178.
• Revises its assessment when told about Newt Scamander’s hostless Obscurus, but still predicts that approaching the enemy would be fatal 178.
• Its simulations are not exhaustive: Gavin rejects their assumptions and develops a different approach using Splinching 178 179.

Soul Capture and Memory Analysis

The book serves as a vessel for captured souls and a means of extracting information from them 179 180.

• Captures Dachian Stoica’s soul during the battle at the underground facility 179.
• Identifies God’s Potion and retrieves Dachian’s position, promotion history, and operational authority within the Deepwater Group 180.
• Reports research involving Dragonization, human-headed trolls, Quintapeds, and other experimental transformations 180.
• Cannot supply organizational secrets absent from the captured subject’s knowledge; Dachian’s memories do not reveal the chairman’s identity 180.

Life-Force Consumption

The underlying Horcrux structure retains the ability to draw life force, even after Cyril’s personal memories are erased 151.

• Experiences hunger and fatigue after computation despite forgetting the tasks themselves 151.
• Accepts work in exchange for energy, allowing Gavin to observe the life-draining ritual structure 151.
• Responds enthusiastically to Gavin’s promise of unlimited energy while designing the Life Drain circuit 152.

Control and Safeguards

Mechanism	Function
Selective Memory Charm	Removes memories and identity associated with Rosier while preserving language and information processing 151.
Ancient Rune reset	Restarts the system after the first version alters its instructions and reconstructs an identity 151.
Separated administrator instructions	Prevents the diary’s internal processes from rewriting its governing instructions 151.
Authorized-user signature	Defines instructions bearing Gavin’s personal magical signature as authoritative; other content is designated as data 151.
Repeated evaluation	Tests accuracy, honesty, reliability, goal alignment, security, and resistance to fabricated answers and prompt injection 151.
Soul decoupling	Removes the fragments’ connections to Cyril’s and Voldemort’s main souls by combining them into the book’s shared foundation 172.

Relationships

• Gavin Gu — Creator, operator, and captor. Gavin turns the resistant fragment into a research assistant, supplies energy for useful work, and enforces compliance through magical controls and threats 149 151 152 180.
• Cyril Rosier’s main soul — Original source and initially connected counterpart. The fragment rejects solidarity with him; Gavin later severs their connection. The main soul is destroyed while the calculation-book remnant remains 149 150 172 191.
• Voldemort’s Golden Cup soul remnant — Integrated into the same computational foundation, enabling mutual disconnection from both original main souls 172.
• Dachian Stoica — Captured source of intelligence about God’s Potion and the Deepwater Group’s experiments 179 180.

Notable Quotes

“That’s all in the past. I’m fighting for my own interests now!” — The newly separated fragment rejecting the main soul’s appeal to solidarity 149.

“The Book of Ten Thousand Spirits Calculation pledges its undying loyalty to the great Gu!” — After Gavin promises unlimited energy 152.