CustomMonsterReplacer

A monster manager for Valheim. Give any vanilla creature a custom 3D model, or turn a vanilla prefab into a brand-new creature of your own, without touching its AI, stats or loot. Everything is managed from a web GUI while the game runs.

A Valheim BepInEx 5 plugin built on Jotunn.

Two kinds of entry

	Replace	Creature
What it does	Swaps a vanilla prefab's visuals in place	Clones a vanilla prefab under a new registered name
AI / stats / loot	Untouched — stays exactly vanilla	Yours to set: health, faction, AI ranges, spawn biomes
Networking	None — purely visual	A real prefab, registered in ZNetScene
Good for	"make the greydwarf look like this"	"add a troll-sized bear that spawns in the Black Forest"

Features

• Monster manager GUI at http://127.0.0.1:8777/ — add and remove entries, tune scale, position and rotation, toggle individual meshes, and set health, faction and spawns.
• GLB models, loaded with a built-in GLB/GLTF parser. Rigged models animate: skin joints are remapped to the vanilla skeleton by name, with a proximity-weighted fallback.
• Animated creatures from Unity AssetBundles, with walk and attack clips.
• Skeleton overlay in the GUI to visualise which bones matched, and a generated Blender auto-weighting script at /armature_script for content creators.
• Auto height fit — scale a model to a target height in metres, or match the source prefab's own height.
• Distance culling, so custom models stop being processed when far away. The log prints distance culler: N custom model(s) in the world; if that number is stuck at 0, culling is broken.
• A pre-1.4 config migrates itself once into the new entry list, so upgrading is silent.

Requirements

• BepInExPack Valheim (automatic)
• Jotunn (automatic)
• Valheim 1.0.16. The mod is built against it; a game update can break its patches and there is no way to detect that from inside the plugin.

Installation

Install through your mod manager. All five payload files must end up in BepInEx\plugins\CustomMonsterReplacer\, next to the DLL — the model and bundle filenames are resolved relative to it.

Manual install: copy CustomMonsterReplacer.dll, trooper.glb, ogre.glb, valheimbear and valheimogre into that folder.

Bundled models

Every entry has its own model, so nothing is ever removed from the folder.

File	Size	Notes
trooper.glb	17 MB	25 parts, skeleton-bound onto the greydwarf rig
ogre.glb	11 MB	Alternative model
valheimbear	42 MB	AssetBundle, BearPlayer, with walk/attack clips
valheimogre	43 MB	AssetBundle, OgrePlayer, troll-sized

The package is ~109 MB, which is large by design: two of those files are Unity AssetBundles, which are already compressed and do not shrink further.

The AssetBundles were built with Unity 6000.0.75f1 exactly, matching the engine in this Valheim build. A different editor version produces bundles that will not load.

How to use

1. Start the game and open http://127.0.0.1:8777/.
2. Add an entry and pick its kind — Replace (target a vanilla prefab) or Creature (clone one, then give it health, faction and spawn entries).
3. Choose a model, then tune scale (auto-fit or manual), position/rotation offsets, and toggle individual meshes. Changes auto-apply and are saved to the config.
4. In-game, summon or spawn the creature and check it against the vanilla one.

Want to use your own model? Export a GLB rigged to a GreydwarfArmature skeleton — download the generated script from /armature_script — and drop it next to the DLL. It will appear in the GUI's model list.

Configuration

A JSON file created next to the DLL on first load: BepInEx\plugins\CustomMonsterReplacer\monsterreplacer_config.json. The GUI owns this file — edit entries in the browser rather than by hand, or your changes will be overwritten on the next save.

{
  "EnableWebServer": true,
  "WebPort": 8777,
  "Monsters": [
    { "Id": "greydwarf", "Kind": "Replace", "TargetPrefab": "Greydwarf",
      "ModelFile": "trooper.glb", "TargetHeight": 2.0, "CullDistance": 60.0 },
    { "Id": "dfgbear", "Kind": "Creature", "TargetPrefab": "Greydwarf",
      "BundleFile": "valheimbear", "BundlePrefab": "BearPlayer", "Health": 120.0 }
  ]
}

Key	Default	Description
EnableWebServer	true	Serve the manager GUI.
WebPort	8777	Port for the GUI.
Monsters	see above	The entry list.
CullDistance	60.0	Metres before a custom model is culled.
UseTargetHeight	true	Auto-fit to a target height.
TargetHeight	2.0	Target height in metres.
ManualScale	0.01	Scale used when auto-fit is off.
PositionX/Y/Z, RotationX/Y/Z	0	Offsets; rotation in degrees.
DisabledMeshes	[]	Mesh names to hide.

Notes & limitations

• The GUI's 3D model preview needs an internet connection (it loads three.js from a CDN). Every other endpoint works offline.
• Skeleton binding applies to the Replace path. Without it, or on a target with no usable skeleton, the model attaches statically and materials fall back to the target's shader — a magenta error material means no shader was found.
• Bundle creatures need their walk/attack clips baked in; a bundle built without them animates as a Generic rig.

Changelog

See CHANGELOG.md.

Support

If this mod has made your journey through the Tenth World a little better, consider tossing a coin into my Ko-fi jar: https://ko-fi.com/draugrforgedgaming. Your support keeps the forge hot and the mead flowing! Skål!