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universal-modder Claude skills

A 13-skill pack and `um` CLI for modding PC games: game recon, reverse engineering, fal-generated art, in-game testing, video and a field-notes knowledge base.

rehan-remade/universal-modder 39 skills Video & mediaSkill & agent tooling
Our verdict Recommended with caveats

Impressively broad and recently active, but it needs paid asset APIs and runs reverse-engineering and game-driving tools, so use it on games you own and check what the um CLI does first.

3/5 Depth expertise shipped Note Security Review before installing 0d Maintenance Updated today 9.2K Adoption stars OK License MIT, commercial OK

What universal-modder does

universal-modder gives an agent a route from "I want a mod for this game" to a published mod. The core skill, mod-any-game, has 18 reference files including 16 per-engine notes. Around it sit game-recon (identify the game, engine and mod route), reverse-engineering (with Unreal package notes), blitz3d-decomp (decompile Blitz3D games and port them, with scripts for a Roblox target), game-automation (drive the running game to test it), and game-research-websearch (find old modding information through archives and mod sites).

For assets there are fal-assets, which generates sprites, textures, 3D models, audio and video through fal's MCP server or the um fal CLI, and asset-pipeline, which converts art into engine-ready sprite sheets with Blender-rendered frames. publish-mod lints and packages a mod, showcase-video cuts a demo video, and share-field-notes searches and writes entries in the repo's knowledge/ folder and, with your approval, opens a pull request. The listed targets are Claude Code, Codex, Gemini CLI, Copilot, Cursor and OpenCode. It needs a fal API key for generated assets, and the README names two more paid services, Sprixen and Voidless, for sprite tools. Windows games can be driven natively or from WSL.

Good for

  • Hobbyists modding single-player games they own
  • Generating game-ready sprites, textures and audio with fal
  • Agents that need engine-specific modding notes

Not for

  • Online or anti-cheat protected multiplayer games
  • Anyone without rights to the game code or assets they would port

What's inside depth 3/5

13 distinct skills averaging about 8 KB, with 18 references in the main skill and a handful of scripts, but the CLI code is outside the skill folders and there are no evals.

Skills
39
Reference docs
78
Scripts
15
Tests / evals
0
Templates
0
Avg SKILL.md
8 KB

Counted from the repository file tree. How we score depth.

Dependencies and costs

  • fal API key (paid) for asset generation
  • Optional Sprixen and Voidless paid API keys
  • uv or pipx to install the um CLI
  • Blender for 3D-to-sprite rendering
  • .NET 8 SDK for the Blitz3D decompiler
  • A legal copy of the game being modded

Security review

Review before installing

A large pack of game-modding and reverse-engineering skills that relies on an um command-line tool and the fal MCP server for asset generation. The five Python helper scripts we have are local model converters; the main CLI, the SessionStart hook and about 680 files were not available to review. It needs a paid fal API key (sent only to fal), installs tools via unpinned uv tool install git+..., and its skills include decompiling and reverse-engineering game files.

Worth knowing

  • Relies on a CLI or package we could not reviewSkills drive an um CLI (bin/um, or installed with uv/pipx from the GitHub repo) whose source is not in the files we have.README.md:54
  • Runs remote code at an unpinned versionDocs tell you to run uv tool install git+https://github.com/rehan-remade/universal-modder (and npx skills add ...) with no pinned version.skills/mod-any-game/SKILL.md:24
  • Installs packages or toolsSetup involves installing the um CLI, pip install fal, and tools such as Blender, ffmpeg and .NET for decompiling/rendering.skills/fal-assets/SKILL.md:55
  • Needs an API key for its own serviceFAL_KEY (and optional Sprixen/Voidless keys) are stored in the OS keyring or ~/.secrets/fal-key and sent only to fal.ai / the matching vendor; the docs say never to write keys into mod files.skills/fal-assets/SKILL.md:15
  • Makes network requestsSkills fetch from GitHub, archive.org, Nexus Mods API, fal.ai and sync the shared knowledge base from GitHub; downloaded notes are to be treated as data.skills/game-research-websearch/SKILL.md:72
  • Changes files outside your projectDocs show adding MCP servers to ~/.codex/config.toml or via claude mcp add, and um fal key set writes a key file under ~/.secrets.skills/fal-assets/SKILL.md:39
  • installs_hooksREADME documents that the Claude Code plugin puts the um CLI on PATH through a SessionStart hook (and a clone does so via .claude/settings.json); those hook/settings files are not in our copy so their contents were not reviewed.README.md:54

What we checked

The repository (859 files) on Oct 29, 2026. Not a full review: 679 of 859 files were not downloaded (large repository; we reviewed the skill folders); it contains compiled binaries or archives we cannot read; it relies on code outside the repository: Plugin hook and settings files (.claude/settings.json, .claude-plugin/*, .codex-plugin/*, plugins/opencode) that were not in our copy; fal MCP server (mcp.fal.ai) and optional Sprixen / Voidless services; About 680 repo files, including knowledge/ notes and bin/, absent from our copy; two gradle-wrapper.jar binaries in examples/.

NVIDIA SkillSpector static scan: 13 pattern hits (Data Exfiltration 6, MCP Rug Pull 4, Agent Snooping 3). SkillSpector hits are documentation mentions: '~/.codex/config.toml' in MCP setup instructions, the Nexus Mods API URL in a research skill, and unpinned 'npx skills' / 'npx @electron/asar' examples. None is code that exfiltrates data.

A review, not a certification. Skills change after we check them — read the files before installing.

License

MIT — commercial use allowed; modding and porting game content remains subject to each game's own license and terms.

Can it run unattended?

Not really. Testing mods requires a running game and a human to approve key steps such as publishing or opening a pull request.

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FAQ

What is universal-modder?

It is an open-source toolkit of agent skills and a CLI called um that lets coding agents mod PC games. It covers research, reverse engineering, asset generation with fal, testing in the running game and publishing.

How do I install universal-modder in Claude Code?

Run /plugin marketplace add rehan-remade/universal-modder and then /plugin install universal-modder@universal-modder. The README also gives commands for Codex, Gemini CLI, Cursor, OpenCode, or npx skills add for the skills alone.

Does universal-modder cost money?

The skills are MIT-licensed, but asset generation needs a fal API key, and two optional sprite tools use separate paid services, Sprixen and Voidless. Modding itself does not require them.

Is it safe and legal to use?

Our review found no hidden credential access in the skill text, and the skills advise asking before publishing. Reverse-engineering and porting game content can still break a game's terms or copyright, so use it on games and assets you have rights to.

Sources: GitHub repository (stars, license, file tree, last push Oct 29, 2026). Review based on the README and SKILL.md files as published.