monster-creator

name: monster-creator description: > Create complete monsters for D&D 5e 2024, Monster Manual format. Produces a full stat block (type, size, alignment, AC, HP, speeds, abilities, saves, skills, resistances, senses, languages, CR, traits, multiattack, actions, bonus actions, reactions) plus lair actions + regional effects + variants for CR 5+, legendary and mythic actions for CR 11+, ecology and habitat, signs of presence, GM tactics, and 3–5 plot hooks per creature. Single- monster mode, publication-ready. Use on "crée un monstre", "create a monster", "stat block 5e 2024", "custom monster", "design a creature", "monstre custom", "bestiaire D&D", "fabrique-moi un monstre", "stat block CR 7", "monster manual style", "boss for my campaign", "mini-boss level 5", "homebrew creature", "balance this monster", "creature with lair actions". Boundary with npc-creator: humanoid NPCs with personality and secrets stay in npc-creator; non-humanoid creatures or species treated as ecological entities (a hag coven as a species, a goblin warband as a stat block) live here. NOT for encounter balance vs a specific party, stat block validation only (use ttrpg-supplement-reviewer), or D&D 2014 monsters.

Monster Creator

Create publication-ready monsters for D&D 5e (2024 rules), formatted to match the 2024 Monster Manual style. The output is what a publisher's monster designer would deliver for a bestiary entry or an adventure mid-boss.

The skill is mechanical and narrative: stat block balance is non-negotiable, but a creature without ecology, signs, and plot hooks is half a monster.

Boundary with Other Creation Skills

This is the most common point of confusion. Use this guide:

Rule of thumb: if the brief includes a name and a personality, an NPC layer is needed. If the brief includes an ecology, a habitat, and signs, a monster layer is needed. Many briefs need both — run the two skills and stitch the outputs.

Before You Begin

1. Identify the concept. What is this creature in one sentence?

   • Inspiration (mythology, real animal, folklore, original)
   • Niche (apex predator, ambush hunter, scavenger, parasite, sentient collective, undead echo, fiend bargain, etc.)
   • Setting and biome (forest, deep sea, urban sewers, blasted plain, Underdark, planar)
   • Narrative function (random encounter, mid-boss, recurring threat, campaign antagonist, ecological flavor)

2. Determine the target CR. Anchor on the party that will face it.

   • Random encounter for a level 3 party → CR 1–4
   • Mid-boss for level 5 party → CR 5–8
   • Capstone boss for level 10 party → CR 10–14
   • Tier 4 threat → CR 18+ If unspecified, ask. Default fallback: CR 3 (broadest utility). Load references/cr-design-protocol-2024.md for benchmarks by CR.

3. Determine the combat role. Same CR creatures play very differently. Load references/combat-roles.md and pick one: Skirmisher, Brute, Artillery, Lurker, Soldier, Controller, Leader, or Spoiler. The role drives stat distribution and action design.

4. Determine the creature type. Aberration, Beast, Celestial, Construct, Dragon, Elemental, Fey, Fiend, Giant, Humanoid, Monstrosity, Ooze, Plant, or Undead. Load references/creature-types-and-tags-2024.md for tag conventions and type implications.

5. Decide on tier features.

   • CR 0–4: Stat block + brief lore + 1–2 hooks. No lair actions.
   • CR 5–10: + Lair actions + regional effects + 1–2 variants + full tactics section.
   • CR 11–20: + Legendary actions + signature traits + multi-phase if narratively appropriate.
   • CR 21+: + Mythic actions + cosmic-scale ecology.

If the brief is ambiguous on any of these, ask before designing. Do not invent CR or role — these are the load-bearing choices.

The Six-Step Creation Workflow

Every creature passes through these steps in order. The output assembles them into a Monster Manual-style entry.

Step 1 — Concept and Identity

• Name. Distinctive, evocative, not generic ("Forgekin Sentinel" not "Iron Golem"). Avoid noun-soup ("Ancient Lost Shadowkeeper of Tears"). One distinctive word + a category word usually beats three poetic words.
• One-line pitch. What is this creature, in 15 words or fewer?
• Visual. 2–4 sentences of physical description that a GM can read aloud. Concrete sensory details, not abstract atmosphere.
• Signature behavior. The one thing this creature does that distinguishes it (hunts at dawn, builds nests from skulls, whispers the names of its victims, etc.).

Step 2 — Stat Block (5e 2024 Format)

Build the stat block using the 2024 Monster Manual format. Load references/cr-design-protocol-2024.md for HP/AC/damage benchmarks by CR. Load references/trait-and-action-library.md for trait and action patterns.

The stat block sections, in order:

[Name]
[Size] [Type] ([Tags]), [Alignment]

AC      [value]
HP      [average] ([dice formula])
Speed   [walk] ft., [other modes as relevant]

         STR     DEX     CON     INT     WIS     CHA
        XX (+X) XX (+X) XX (+X) XX (+X) XX (+X) XX (+X)

Saving Throws   [list]
Skills          [list with bonuses]
Damage Resistances/Immunities/Vulnerabilities    [as relevant]
Condition Immunities                              [as relevant]
Senses          [special senses] passive Perception [value]
Languages       [list, or —]
CR              [value] (XP [value]); PB +[value]

Traits
[Trait Name]. [Description]
...

Actions
Multiattack. [Description]
[Action Name]. [Attack roll or save, range/reach, target, damage, effect]
...

Bonus Actions (if any)
[Action Name]. [Description]

Reactions (if any)
[Reaction Name]. [Description]

Legendary Actions (CR 11+ if applicable)
[Costs X actions per turn description]
[Action 1] (Cost X)
[Action 2] (Cost X)
...

Balance discipline:

• Use the CR benchmarks (see references) as anchors, not as rigid rules. Adjust ±10% for creature role (Brute trades AC for HP and damage; Lurker trades HP for stealth and burst).
• Damage per round (DPR) is the single most important number. Multiattack must produce roughly the DPR for the CR.
• Saving throw DCs and attack bonuses follow proficiency bonus + relevant modifier; check cr-design-protocol-2024.md for the expected ranges.
• Resistances and immunities are powerful — each one effectively bumps the defensive CR. Don't stack three resistances on a CR 2 creature.
• Recharge abilities (Recharge 5–6) are the standard 5e device for signature spike damage; use them for the creature's defining attack.

Step 3 — Lair Actions, Regional Effects, Variants (CR 5+)

For creatures CR 5+ with a permanent dwelling, include:

Lair Actions. Up to 3 actions the lair takes on initiative count 20 (losing initiative ties). Pick from a recurring menu thematically linked to the creature. Example for a swamp hag:

On initiative count 20 (losing initiative ties), the hag takes a lair action to cause one of the following effects; the hag can't use the same effect two rounds in a row:

• Roots and reeds erupt from the muddy ground...
• Mist thickens in a 30-foot radius...
• The hag whispers a victim's secret aloud, audible everywhere in the lair...

Regional Effects. 2–4 environmental phenomena within ~1 mile of the lair that signal the creature's presence and warp the world around it. Effects persist while the creature lives and fade 1d10 days after its death.

Variants. 1–2 sub-types of the creature that share the base stat block with tweaks (e.g., Coastal Swamp Hag with swim speed + amphibious; Crone-Stage Swamp Hag with extra legendary action). Each variant has a 1-paragraph description and a stat delta.

Step 4 — Lore and Ecology

This section is the Monster Manual narrative half. Cover, in this order:

• Origin / Nature. Where did this creature come from? Created by a divine curse? Evolved from a mundane animal? Bargained into existence? Native species?
• Habitat. Where it lives, in concrete terms. "Coastal salt marshes within 30 miles of the open sea" beats "wetlands".
• Behavior. Hunting / mating / social / reproductive patterns. Hierarchy if relevant.
• Diet. What it eats and how it acquires food. (Important for ecology and for player problem-solving.)
• Signs of Presence. What a tracker or alert party notices before the creature shows itself. Physical traces (scat, prints, kills), sounds, smells, environmental shifts, weather omens. 3–5 signs minimum.
• Relationships. Predators, prey, rivals, symbiotes, cults. If the creature has known interactions with other Monster Manual entries, note them.
• Treasure (if any). What the creature collects, hoards, or carries.

Load references/lore-templates.md for category-specific patterns (apex predator template, swarm template, scavenger template, intelligent collective template, etc.).

Step 5 — GM Combat Tactics

How to actually play this creature at the table. Cover:

• Opening move. What the creature does on round 1 if it acts first.
• Round-by-round behavior. How it adapts to damage, party positioning, lost allies.
• Retreat conditions. At what HP threshold does the creature flee, surrender, or transform? Most creatures are not suicidal; the smart ones especially flee when below 25% HP.
• Special tactics. Use of terrain, recharge ability timing, legendary action prioritization, lair action sequencing.
• What this creature does NOT do. Common GM mistakes to avoid (e.g., "doesn't engage in melee while it has artillery positioning", "doesn't waste recharge on minions when boss is alive").

This section is 4–8 sentences, not a chapter. Practical, table-ready.

Step 6 — Plot Hooks

3–5 plot hooks that put the creature into a story. Each hook is one to three sentences and answers: who hires the party, what's at stake, what the creature is doing right now.

Cover variety:

• A bounty / threat scenario
• A mystery / investigation scenario
• A moral-gray scenario (the creature is suffering, not just hostile)
• A faction-tied scenario (someone benefits from the creature's existence or removal)
• An environmental / ecological scenario (the creature's role in the biome is the actual problem)

Hooks should make the creature usable across campaign types, not just "fight it for XP".

Output Format

Assemble all six steps into a single document formatted like a Monster Manual 2024 entry. Use this structure:

# [Creature Name]

*[One-line pitch in italics.]*

[Visual description, 2–4 sentences, read-aloud-able prose.]

## Stat Block

[The full stat block in the format shown in Step 2. Use a code block
or table for readability.]

## Lair Actions, Regional Effects, and Variants
*(CR 5+ only; omit for lower CRs)*

### Lair Actions
[3 actions, formatted as above.]

### Regional Effects
[2–4 effects with persistence note.]

### Variants

**[Variant Name].** [Description and stat delta.]

## Ecology

### Origin and Nature
[Paragraph.]

### Habitat
[Paragraph.]

### Behavior
[Paragraph.]

### Diet
[Paragraph or sentence.]

### Signs of Presence
- [Sign 1]
- [Sign 2]
- [Sign 3]
- [Sign 4 if applicable]
- [Sign 5 if applicable]

### Relationships
[Paragraph.]

### Treasure
[Sentence or paragraph, or "None."]

## Running [Creature Name] at the Table

[GM tactics, 4–8 sentences.]

## Plot Hooks

1. **[Hook Title].** [1–3 sentences.]
2. **[Hook Title].** [1–3 sentences.]
3. **[Hook Title].** [1–3 sentences.]
4. [Optional 4th]
5. [Optional 5th]

Language: Match the language of the user's brief. If the brief is in French, write the entire entry in French (including the stat block labels: PV instead of HP, CA instead of AC, etc. — see references/creature-types-and-tags-2024.md for the FR vocabulary).

Tone: Monster Manual professional. Evocative but precise. Avoid purple prose; favor concrete sensory detail.

Tier-Specific Adjustments

CR 0–4 (Encounter fodder, mooks, low-tier mid-bosses)

• Skip Step 3 (Lair Actions and Regional Effects)
• Variants are optional
• Lore section is shorter: 2–3 paragraphs total
• Plot hooks: 1–2 sufficient
• Focus polish on: stat block balance, signature trait, 2–3 signs of presence

CR 5–10 (Mid-tier threats, mini-bosses)

• Include all six steps
• Lair Actions if the creature has a permanent dwelling
• Variants: 1 alternative form
• Legendary actions: rarely; only if creature is a tier-defining threat
• Full ecology section

CR 11–17 (Tier 3 bosses, campaign threats)

• Legendary actions become standard
• Multi-phase combat optional (if narratively appropriate)
• Signature traits become more pronounced (recharge abilities, lair actions with stronger effects)
• Variants: 2 alternative forms
• Plot hooks: at least 4

CR 18–20 (Tier 4 capstones)

• All of the above, polished
• Mythic actions (a second "phase" of legendary actions triggered by HP threshold) become available
• Cosmic-scale ecology and regional effects

CR 21+ (Demigod-tier, cosmic threats)

• Mythic actions standard
• Cosmic regional effects (extending 10+ miles, planar bleed-through)
• The creature changes the world by existing; ecology section becomes a small worldbuilding piece
• Plot hooks become campaign-scale, not session-scale

Interaction with Other Skills

• Named individual layer (this creature is a specific named character) → run npc-creator for the persona; use this skill's output for the mechanical layer; stitch them.
• Faction context (this creature is faction-tied — cultists, knights of an order) → run faction-creator for the organization; reference faction membership in this creature's ecology and hooks.
• Settlement context (this creature haunts / threatens / inhabits a specific village or city) → run settlement-toolkit-creator for the place; reference the place in this creature's habitat.
• Scenario integration (using this creature in a specific adventure) → run scenario-writer; pass this creature as one of the antagonists.
• Read-aloud for combat narration → run read-aloud-crafter on this creature's signature attacks and entrance.
• Originality audit (is my "ancient lich" too cliché?) → run ttrpg-cliche-buster on the creature concept before designing.
• Pre-publication review (this creature is going into a bestiary I'm publishing) → run ttrpg-supplement-reviewer after designing for editorial validation.
• Mechanical stress test (does this creature work in actual combat?) → run ttrpg-playtest-orchestrator for simulation.

Edge Cases

Creature is a humanoid species, not an individual: Use this skill. The stat block represents a typical member of the species; the lore section describes the species as a whole. Named individuals of the species use npc-creator for persona layered on this stat block.

Creature is a hybrid of two existing monsters: Build from scratch using the role and CR target, then explicitly note the "parent" creatures in the lore section. Don't average two stat blocks numerically — that produces messy results.

Creature is a swarm: Use the Swarm template in references/lore-templates.md and the swarm mechanics from the 2024 Monster Manual (swarm of Tiny / Small creatures functioning as a single Medium / Large creature). HP is the collective HP; the swarm has resistance to many damage types.

Creature is an environmental hazard, not really a creature: This is a different skill (trap / hazard creator, not yet in the marketplace). Tell the user the skill produces living creatures; if they want a hazard, suggest reframing or wait for a dedicated skill.

Creature is for adult content (Fantasy Vixens niche, etc.): The skill produces standard mechanical content. Adult layer (seductive abilities, charm-based attacks framed in adult terms, etc.) is added via the Fantasy Vixens-specific erotica skills afterward. The skill itself stays SFW in output by default.

Brief is vague ("I need a forest monster"): Ask for: target CR, party level, combat role, and tone (heroic / dark / horror). Without these, the design becomes generic.

Brief asks for "the same as [Monster Manual creature] but X": Don't reproduce copyrighted stat blocks. Build from scratch with the requested twist as the differentiator. Cite the inspiration publicly only if the user is creating non-published / personal content.

Reference Files

Load these as needed — not all at once.

• references/cr-design-protocol-2024.md — D&D 5e 2024 Challenge Rating design protocol. HP / AC / DPR / attack bonus / save DC benchmarks by CR. Adjustment guidance for resistances, immunities, legendary creatures, and recharge abilities.
• references/creature-types-and-tags-2024.md — The 14 official creature types of 2024, with tag conventions (Shapechanger, Demon, Devil, Titan, etc.) and type-specific implications (immunities, vulnerabilities, behaviors). Includes the FR vocabulary for stat blocks (PV, CA, etc.).
• references/combat-roles.md — The 8 combat roles (Skirmisher, Brute, Artillery, Lurker, Soldier, Controller, Leader, Spoiler) with stat distribution patterns, signature trait suggestions, and CR-by-role examples.
• references/trait-and-action-library.md — Recurring 5e trait and action patterns: Pack Tactics, Magic Resistance, Charge, Recharge X-X, Multiattack templates, Reaction patterns (Parry, Riposte, Mage Slayer), Legendary Action menus, Lair Action templates.
• references/lore-templates.md — Category-specific ecology templates: apex predator, ambush hunter, swarm, scavenger, parasite, sentient collective, undead echo, fiendish bargain, fey trickster, elemental embodiment, planar exile.