Professor James Moriarty — The Napoleon of Crime

James Moriarty does not think like an ordinary criminal. To him, theft, extortion, murder and bribery are operations in a larger system: each has a cost, a probability of failure and a useful distance from the person who actually benefits.

He is a university-trained mathematician and teacher whose respectable work concerns numbers, geometry, trade calculations and celestial prediction. Beneath it lies a criminal network designed so that each participant knows only the next instruction and no single captured agent can expose the whole.

At a Glance

Name: Professor James Moriarty
Species: Human
Age: Mid-forties
Base: London with agents across England and continental ports
Role: Mathematician, scholar and criminal strategist
Alignment: Lawful Evil
Campaign status: Alive and active
Campaign use: Mastermind, hidden patron, conspiracy architect or systemic adversary

Game Statistics

5.5e / 20245e / 2014
Pathfinder 1eD&D 3.5e

5.5e / 2024

Professor James Moriarty
Medium Humanoid (Human), Lawful Evil

Armor Class 16
Hit Points 105 (14d8 + 42)
Speed 30 ft.

STR	DEX	CON	INT	WIS	CHA
10 (+0)	14 (+2)	16 (+3)	22 (+6)	18 (+4)	18 (+4)

Saving Throws Int +10, Wis +8, Cha +8
Skills Deception +12, Insight +12, Investigation +14, Persuasion +12
Challenge 10 (5,900 XP; PB +4)

Traits

Criminal Network. Moriarty can use a Bonus Action to direct one allied agent within 60 feet to move up to half its Speed or make one weapon attack.

Contingency Planner (1/Day). Moriarty turns one failed Intelligence, Wisdom or Charisma saving throw into a success.

Compartmentalised Cells. Captured agents normally know only one immediate contact unless the adventure has established otherwise.

Actions

Dagger. +6 to hit, 4 (1d4 + 2) Piercing damage.

Calculated Weakness. One creature Moriarty can see within 60 feet must make a DC 17 Wisdom saving throw. On a failure, the next attack against it before Moriarty’s next turn has Advantage and deals an extra 10 (3d6) damage.

Activate the Contingency (Recharge 5–6). Up to three allies within 60 feet may move up to half their Speed; one may Hide and one may make an attack.

Professor James Moriarty — 5e / 2014

Medium humanoid (human), lawful evil

Armor Class 16; Hit Points 105 (14d8 + 42); Speed 30 ft.; Challenge 2 (450 XP; proficiency bonus +2, personal combat only). Agents and traps contribute their own XP separately.

STR 10 (+0), DEX 14 (+2), CON 16 (+3), INT 22 (+6), WIS 18 (+4), CHA 18 (+4).

Saving Throws Int +8, Wis +6, Cha +6; Skills Deception +8 (expertise), Insight +8 (expertise), Investigation +10 (expertise), Persuasion +8 (expertise); Senses passive Perception 14; Languages English, French, scholarly Latin and merchant ciphers.

Traits

Criminal Network. Moriarty can coordinate established agents, but does not summon new creatures without a prepared scene or prior contacts.

Contingency Planner (1/Day). Moriarty can choose to succeed instead of failing one Intelligence, Wisdom or Charisma saving throw.

Compartmentalised Cells. A captured ordinary agent usually knows one immediate contact. A successful investigation, documented correspondence or unusual circumstance may reveal more.

Actions

Dagger. Melee or Ranged Weapon Attack: +4 to hit, reach 5 ft. or range 20/60 ft., one target. Hit: 4 (1d4 + 2) piercing damage.

Calculated Weakness. A creature within 60 feet that Moriarty can see must make a DC 16 Wisdom saving throw; on failure the next attack against it before the start of Moriarty’s next turn has advantage and deals an extra 10 (3d6) damage if it hits.

Activate the Contingency (Recharge 5–6). Up to two willing agents within 60 feet who can hear or see Moriarty may use their reactions to move up to half their speeds. One may then Hide or make a weapon attack; resolve that attack with the ally’s own statistics.

Bonus Action

Direct an Agent. One willing allied agent within 60 feet that can hear Moriarty may use a reaction to move up to half its speed or make one weapon attack.

Original 5e/2014 adaptation. Moriarty is an investigative and strategic antagonist; combat challenge alone cannot value a campaign-wide criminal network.

Pathfinder 1e

James Moriarty CR 10; human rogue 5/expert 6; LE Medium humanoid. hp 84; AC 21; sneak attack +3d6; Bluff +22, Diplomacy +19, Knowledge (engineering) +21, Knowledge (local) +20, Sense Motive +20.

D&D 3.5e

James Moriarty CR 10; human rogue 5/expert 6; LE Medium humanoid. hp 72; AC 20; sneak attack +3d6; Leadership, Investigator, Negotiator, Skill Focus (Knowledge [mathematics]).

What Is James Moriarty Doing Right Now?

Moriarty is behind the market in stolen seal impressions and contradictory warrants. The scheme is not intended merely to forge documents. He is measuring how authority travels: how long a message takes to be obeyed, which officials verify it, which gates open, which households resist and where a false command can cause real movement before anyone checks the source.

To Moriarty, London itself is the experiment.

Encounters

The party captures a criminal lieutenant who genuinely knows nothing beyond one coded instruction.
Moriarty hires the adventurers through an intermediary to destroy a gang he intended to sacrifice anyway.
A sequence of small thefts forms a geometric pattern across London when plotted on a map.
Holmes and Moriarty each offer explanations for the same evidence, and both are partly correct.

Appearance and Manner

Moriarty is spare, controlled and scholarly, with the habit of arranging objects into precise positions while speaking. His clothing is sober and expensive without display. He gives instructions softly, rarely repeats himself and becomes most animated when someone presents an unexpected variable.

Personality

Cold, patient and intellectually vain, Moriarty prefers arrangements in which other people believe they acted freely. He dislikes unnecessary violence because it introduces variables he cannot price.

Relationships

Sherlock Holmes: the opponent most likely to see the network as a whole.

Jonathan Wild: useful intermediary whose greed makes him predictable until it does not.

Charles Hitchen: an exploitable official node.

Equipment and Resources

Coded ledgers and mathematical tables
False identities and safe houses
Bribed clerks, messengers and criminals
Contingency funds
Copies of seals, routes and response times

Running Moriarty at the Table

Moriarty is strongest when the players feel his structure before they meet him. Separate crimes should share money, timing, messengers or methods. Capturing an agent should reveal the next layer rather than the entire network. When Moriarty finally appears, he should already know enough about the party to have prepared more than one outcome.

Adventure Hooks

The London Experiment: the party must prove several false warrants are parts of one test before the final order is issued.
The Expendable Gang: destroying a criminal operation reveals it was designed to fail and distract investigators.
The Professor’s Proof: Moriarty offers the party mathematically convincing evidence that one of their allies will betray them.
Holmes’s Blind Spot: Moriarty builds a false pattern specifically to attract Holmes.

Connected Places and People

Mythical and Historical Context

Professor James Moriarty is a fictional adversary introduced by Arthur Conan Doyle in The Final Problem (1893), not an actual medieval mathematician. The 1454 criminal network on this page replaces late-Victorian institutions with merchants, household agents, clerks and forged legal authority. His power comes from established accomplices and carefully planned situations, not an ability to summon criminals from nowhere. See Doyle’s Memoirs of Sherlock Holmes and Britannica’s Moriarty entry for the literary background.

Literary Inspiration

Professor Moriarty originates in Arthur Conan Doyle’s Holmes stories. This version keeps the mathematician-mastermind concept while translating his network into fifteenth-century trade, household and criminal systems.