A free D&D 5.5e (2024 rules) toolkit for Dungeon Masters: build balanced encounters, forecast the battle before your party rolls initiative, and run the whole session — prep tools, live battle support, and searchable SRD rules in one place.
Platform direction: Encounterizer is moving from its current browser-only static build to a server-authoritative, cloud-native application on Cloudflare. See the Cloudflare Cloud-Native Roadmap.
- ⚔️ Encounter Builder — Set party size, level, and difficulty; get a balanced encounter with monsters, scenario hook, tactics, treasure, and an optional battle map. Uses the real 2024 DMG XP budgets (Low/Moderate/High — no 2014 multipliers). Every generated encounter is seeded: Copy Link produces a URL that regenerates the exact same encounter for anyone. Save named encounters for later sessions.
- 🔮 Battle Forecast — One click runs 1,000 Monte Carlo battle simulations against your actual party (pick class templates and levels, tweak the numbers if you like). Get the win rate, expected rounds, round-by-round HP curve, who's most likely to drop, and an honest "the XP says Moderate, but this plays like Deadly" assessment. It's a weather forecast, not a promise — but no mainstream encounter builder does it.
- 🐉 Monster Bestiary — 331 monsters from the SRD 5.2.1 (genuine 2024 stat blocks), each with a dedicated portrait, plus deep filtering: CR, type, size, environment, movement modes, damage types dealt, resistances, immunities, conditions, legendary/spellcaster/lair toggles. Import your own monsters from 5etools bestiary JSON or Encounterizer exports — stored locally in the current build and moving to private campaign-scoped cloud storage.
- 🗺️ Map Generator — Procedural battle maps: BSP room-and-corridor dungeons, cellular-automata caves, and environment-specific outdoor terrain. Export as JSON or ASCII.
- 🧩 Puzzles & Challenges — One seeded generator: verified logic/word/spatial puzzles, riddles, ciphers, contests, plus social encounters, journeys, traps, chases, and investigations.
- 🛡️ DM Screen — Build a private command screen from monsters, spells, rules, notes, tool links, and a compact live battle tracker.
- ⚔️ Battle Organizer — Sort initiative and track HP, conditions, concentration, reactions, legendary actions, rounds, and turn flow.
- 📖 Reference Library — One searchable home for 200 SRD rule articles, 12 classes, 12 subclasses, 339 spells, 182 equipment entries, 257 magic items, 17 feats, 4 backgrounds, and 9 species. Use category-specific filters, open focused printable details, and bookmark anything for later. Import your own spells from 5etools spell JSON or Encounterizer exports — stored locally in the current build and moving to private campaign-scoped cloud storage.
Every prep page has a Print button with a dedicated print stylesheet — clean, ink-friendly handouts straight from the browser. The current build persists settings and workspace data in browser storage; the cloud-native milestones replace that persistence with authenticated D1, R2, and Durable Object services.
| Layer | Technology |
|---|---|
| Framework | Next.js 16 App Router on Cloudflare Workers through OpenNext |
| Language | TypeScript (strict) |
| Styling | Tailwind CSS + CSS custom properties (Dusksteel tokens), Spectral + IBM Plex Sans via next/font, Lucide icons |
| Current data | D1-backed identity/campaign tenancy plus generated SRD data and transitional browser tool persistence |
| Target platform | Cloudflare Workers/OpenNext, D1, R2, Durable Objects, Queues, and Workflows |
| Testing | Vitest in Node and workerd (rules math, importer, Monte Carlo statistics, Worker integration) |
| CI/CD | Cloudflare Workers Builds plus protected GitHub Actions staging/production promotion |
src/
app/ # Next.js App Router (static and server-rendered routes)
page.tsx # Landing page (stats computed from data modules)
encounters/ # Encounter Builder + Battle Forecast
monsters/ # Bestiary + custom monster import
maps/ # Map Generator
noncombat/ # Puzzles & Challenges
dm-screen/ # Configurable DM command screen
battle/ # Live initiative and combat organizer
reference/ # Unified rules, classes, gear, spells, items, and character reference
compendium/, spells/ # Compatibility routes into the unified reference
credits/ # SRD attribution + licensing
icon.svg, opengraph-image.png, robots.ts, sitemap.ts
components/
NavBar.tsx # Responsive nav with active states
FilterPanel.tsx # Full-criteria monster filter UI
MonsterStatBlock.tsx # 5e-style stat block renderer
MapGrid.tsx # Grid map display with terrain legend
PartySetupPanel.tsx # Battle Forecast party configuration
BattleReportCard.tsx # Forecast results (SVG donut + HP curve)
CustomMonsterPanel.tsx # JSON import / manage custom monsters
DifficultyBadge.tsx, PrintButton.tsx
lib/
types.ts # Core type system + 2024 XP budget table
encounter-generator.ts # Budget math, knapsack selection, hooks/tactics/treasure
battle-sim.ts # Seeded Monte Carlo combat engine
monster-to-sim.ts # Stat block → simulator stats extraction
monster-filter.ts # Search/filter engine
map-generator.ts # BSP + cellular automata + outdoor scatter
noncombat/generate.ts # Unified orchestrator: puzzles & challenges (one seeded gen)
encounter-recipes.ts # Recipe-based encounter templates (engine)
import-5etools.ts # 5etools JSON → Monster converter (2024 format)
custom-monster-import.ts # Client-side JSON import with validation
random.ts # Shared seeded RNG (shareable-link determinism)
storage.ts # SSR-safe localStorage utility
data/
monsters-*.ts # AUTO-GENERATED SRD 5.2.1 bestiary (7 CR bands)
bestiary-meta.ts # Generated count + source commit
class-templates.ts # Battle Forecast class builds (15 × 4 tiers)
spells.ts # Spell type + search/filter helpers (aggregates the bands)
spells-l*.ts # AUTO-GENERATED SRD 5.2.1 spells (4 level bands)
spells-meta.ts # Generated count + source commit
spell-summaries.ts # Hand-curated effect summary overrides
reference-articles.ts # AUTO-GENERATED SRD rules and toolbox chapters
classes.ts # AUTO-GENERATED SRD classes and subclasses
equipment.ts # AUTO-GENERATED SRD weapons, armor, gear, tools, and vehicles
magic-items-*.ts # AUTO-GENERATED SRD magic items (rarity bands)
feats.ts # AUTO-GENERATED SRD feats
backgrounds.ts # AUTO-GENERATED SRD backgrounds
species.ts # AUTO-GENERATED SRD species
scripts/
import-bestiary.ts # Regenerates monster data from 5etools (npm run import:bestiary)
import-spells.ts # Regenerates spell data from 5etools (npm run import:spells)
import-srd-content.ts # Regenerates rules, classes, equipment, items, feats, and origins
- Node.js 20+
- npm
git clone https://github.com/Daren9m/Encounterizer.git
cd Encounterizer
npm install
npm run devOpen http://localhost:3000.
npm run dev # Development server
npm run build # Production Next.js application build
npm run typecheck # tsc --noEmit
npm run lint # ESLint (next/core-web-vitals)
npm test # Vitest suite
npm run import:bestiary # Regenerate the SRD bestiary from the pinned source
npm run import:spells # Regenerate the SRD spell reference from the pinned source
npm run import:srd # Regenerate structured SRD content from pinned Markdown
npm run srd:check # Audit every committed SRD corpus (no network)
npm run cf:build # Build the full-stack OpenNext Worker
npm run cf:test # Exercise the bundled Worker and D1 inside workerd
npm run cf:d1:migrate:local # Apply D1 migrations to local emulationCloud identity and campaign development requires Wrangler bindings. Copy
.dev.vars.example to .dev.vars, replace the placeholder auth secret, run
npm run cf:d1:migrate:local, then use npm run preview. See the
CF-2 identity and authorization runbook
for environment provisioning and promotion.
331 monsters from the System Reference Document 5.2.1 — the
CC-BY-4.0-licensed subset of the 2024 Monster Manual — spanning CR 0 (Frog)
to CR 30 (Tarrasque), with genuine 2024 stat values. The data files are
generated by scripts/import-bestiary.ts from a pinned 5etools source
commit and never edited by hand; an audit gate fails the import on
unstripped formatting tags, lost attacks, or missing XP.
Want more? The Bestiary page imports additional monsters from 5etools bestiary JSON or Encounterizer's own export format — converted and validated entirely in your browser, never uploaded anywhere.
339 spells from the System Reference Document 5.2.1 — every SRD spell
from cantrips to 9th level, with verbatim 2024 rules text, generated by
scripts/import-spells.ts from a pinned 5etools source commit and never
edited by hand. An audit gate enforces exact corpus counts, licensing name
checks, format whitelists, and field-coverage parity on every regeneration.
The bold one-line effect summaries are layered: hand-curated overrides in
src/data/spell-summaries.ts win over machine-synthesized mechanics lines.
The same reference contains the complete structured rules corpus: 200 rule
articles (including Playing the Game, Character Creation, Equipment Rules,
Spellcasting Rules, the Rules Glossary, the Gameplay Toolbox, and Magic Item
Rules), 12 classes, 12 subclasses, 182 equipment entries, 257 magic items,
17 feats, 4 backgrounds, and 9 species from SRD 5.2.1. Together with the
339 spells, that is 1,032 built-in references. scripts/import-srd-content.ts
parses the pinned SRD-reForged Markdown, applies a small audited correction
ledger for known PDF transcription boundaries, and emits typed,
formatting-free records. The /reference route exposes the complete corpus
with full-text search, resource filters, focused printable detail views, and
browser-local bookmarks. See the pipeline documentation.
Like the bestiary, the Reference Library imports additional spells from 5etools spell JSON or Encounterizer exports — converted and validated entirely in your browser, never uploaded anywhere.
Uses the official 2024 Dungeon Master's Guide encounter-building rules:
- XP Budget per character level and difficulty tier (Low/Moderate/High)
- Raw monster XP compared directly against the budget — the 2024 rules dropped the 2014 monster-count multiplier entirely
- Encounters exceeding the High budget are flagged Extreme (a house label — the DMG defines nothing above High)
- Knapsack-style monster selection that fills the budget with variety
- Every generated encounter embeds its RNG seed: Copy Link produces a URL that regenerates the exact same encounter and map
The encounter generator also produces scenario hooks, per-type tactics, and treasure by CR tier.
The simulator models initiative, attack rolls, crits, multiattack routines, breath-weapon recharges, legendary actions, healing, Rage damage reduction, Sneak Attack, and Evasion. Monster stats are extracted automatically from their stat blocks; caster monsters whose damage lives in spell text get a CR-appropriate damage floor so a Lich never simulates as a pushover. Deliberate simplifications (KO is final, AoE hits two targets) are part of the design — the report brands itself a forecast and lists any approximations it made.
Three procedural algorithms:
- BSP (Binary Space Partition) — dungeon rooms connected by L-shaped corridors, with doors, stairs, traps, treasure, pillars
- Cellular Automata — organic cave systems (Underdark, mountain caves, planar rifts) with guaranteed connectivity
- Outdoor Scatter — environment-specific terrain (forest vegetation, swamp water, desert dunes, arctic ice, rivers with bridges)
Every map comes with keyed rooms — names, DM purposes, and read-aloud text — rendered as a clean-tactical SVG battle map with coordinate rulers and room-number chips. Exports: PNG, Markdown (grid + room key), JSON, ASCII text, and UVTT (.dd2vtt) with line-of-sight walls and door portals for Foundry-style importers.
Maps are seeded and shareable (/maps?seed=…). Maps generated alongside
encounters share the encounter's seed, so shared links reproduce the map,
the room key, AND the suggested token placement (party spawns, monster
zones, boss room). With a map attached, the Battle Forecast runs on the
grid: movement, weapon ranges, difficult terrain, and chokepoints all
shape the outcome, and the report shows rounds-to-contact alongside its
usual statistics.
The application now builds as a full-stack OpenNext Worker with isolated local,
preview, staging, and production configuration. The staging runtime is deployed
at encounterizer-stg,
including live health/readiness APIs and a server-rendered /status page.
Developer, delivery, promotion, log, and rollback commands live in the Cloudflare delivery runbook. The Cloudflare Cloud-Native Roadmap defines the remaining data migration and production cutover; Azure remains only as the temporary public-production baseline until CF-8.
Releases follow Semantic Versioning and are automated
by .github/workflows/release.yml. Conventional commits on main are
collected into a release pull request:
fix:produces a patch release.feat:produces a minor release.- A breaking-change footer (
BREAKING CHANGE:) or!after the commit type produces a major release.
Merging the release pull request updates package.json, package-lock.json,
the changelog, and the release manifest, then creates the matching vX.Y.Z
Git tag and GitHub Release. The deployed site reads its footer version directly
from package.json, so the displayed version and release tag stay aligned.
Repository administrators must allow GitHub Actions to create pull requests under Settings → Actions → General → Workflow permissions.
- Cloud-native authority — Cloudflare services own durable application data, compute, files, and live-session coordination.
- Server-enforced trust — Authentication, authorization, validation, and tenancy boundaries are enforced on the server.
- Deterministic rules core — Official rules math and seeded generation remain testable, versioned, and independent of AI output.
- Cost discipline — Metered features ship with limits, observability, and budget alerts.
- 2024 rules — 5.5e / 2024 encounter math and SRD 5.2.1 stat blocks must remain accurate; DMs rely on these numbers at the table.
- DM-centric — Every feature answers "does this save the DM time during prep or at the table?"
- Legally clean and private by default — The public catalog contains CC-BY-4.0 SRD content; custom non-SRD content remains private unless its owner explicitly shares it.
- No required LLM dependency — Core encounter, reference, and battle workflows continue to work without AI services.
The active platform plan is the Cloudflare Cloud-Native Roadmap, organized as milestones CF-0 through CF-9 with explicit exit gates and issue-shaped work packages.
See GitHub Issues and the milestones for the full product backlog. Existing highlights include:
- Character Import (#10) — Parse D&D Beyond links, PDFs, or sheet images into Battle Forecast parties
- Enhanced Export (#15) — PDF stat blocks (map VTT export shipped with the Map Generator Overhaul)
- Battle Forecast Phase 2/3 — death saves, AoE modeling, save-or-suck conditions, "what if?" suggestions
Please report suspected vulnerabilities privately. See the Security Policy for supported versions, reporting instructions, and disclosure expectations.
- Code: MIT.
- Game content: This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at https://www.dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/legalcode).
- Encounterizer is unofficial fan content, not affiliated with or endorsed by Wizards of the Coast. See the in-app Credits page.