Mantella, CHIM and SkyrimNet (2026): The Skyrim AI NPC Mods Compared — Setup, Cost and What Each Remembers

Skyrim AI NPC mods let you talk to Skyrim’s characters in your own words — by voice or by typing — and hear them answer in their own voices, with replies written live by a language model you choose. In 2026 there are three that matter: Mantella, CHIM and SkyrimNet.

They do the same thing on the surface. Underneath, they are built three different ways and they remember three different ways, and those two differences decide which one suits you. This page compares them from their own documentation and code, explains how to set up the most popular one, and answers the questions everyone asks first — is it free, and will it work on my Xbox?

We haven’t scored these mods. They are not products we rate, and nothing here is a verdict on how good their conversations are. What we can do is read exactly how each one works, and memory is the part we know best: it’s the problem our benchmark measures on every AI game.

Skyrim and Fallout 4 are trademarks of Bethesda Softworks/ZeniMax. Arcanum is independent and unaffiliated with Bethesda and with the authors of every mod named here; names are used only to identify them.

The Short Answers

Which is best? It depends what you want. Mantella is the easiest to start and also covers Fallout 4. SkyrimNet has the most detailed memory and runs entirely inside the game. CHIM adds an AI narrator and personalities that change as you play.
Is it free? All three are free to download. The language model is where any cost comes from — and all three can use free or local models.
Xbox or PS5? No. All three need SKSE, which only exists for the PC versions of Skyrim.
What do I need? A Windows PC, Skyrim on Steam, GOG or VR, SKSE and a few supporting mods, and either a model service account or a GPU good enough to run a model locally.

The Three Mods at a Glance

	Mantella	CHIM	SkyrimNet
How it runs	A separate program (`Mantella.exe`) that starts with the game, with a settings page in your browser	An SKSE plugin plus a separate server application	A single native plugin inside Skyrim, with a settings page in your browser
How NPCs remember	A summary of each conversation, saved per NPC as a text file you can edit	”Long-term memory … employing various techniques”	A private memory store per NPC, recalled by meaning, fading by importance
Models	Local (koboldcpp, text-generation-webui) or OpenAI, OpenRouter and compatible APIs	ChatGPT, koboldcpp, OpenRouter and others	OpenRouter or any OpenAI-compatible endpoint; different models for different jobs
Games	Skyrim SE, AE and VR; Fallout 4	Skyrim	Skyrim SE, AE and VR
Licence	AGPL-3.0 (open source)	GPL-3.0 (open source)	Not stated in its public repository
Latest activity	v0.14 released 21 April 2026	Repositories updated September 2026	Repository updated September 2026

From each project’s own documentation and GitHub repositories, checked 26 September 2026.

The Two Differences That Actually Matter

How it’s built: one program, a server, or inside the game

Mantella runs a separate program alongside Skyrim. According to its documentation, it “quietly launches in the background when you start the game,” and its settings live in a browser page at localhost:4999. Mantella’s troubleshooting guide notes that this separate program is also where most problems start: antivirus or firewall blocking Mantella.exe from connecting to the game is its most common fix.

CHIM splits the work between a plugin in the game and the CHIM Server, which its repository describes as “a bridge between the SKSE plugin and various AI providers of text-to-speech, speech-to-text, and AI-based chat generators.” The server is a web application in its own right, so there is more to set up and keep running.

SkyrimNet is built to avoid both. Its README says it “is the only project of its kind that runs as a single SKSE plugin. No WSL. No Python launcher. No background server window to keep alive.” Because it lives inside the game, it can read “game state … straight from memory” rather than passing it between programs. Its settings page is at localhost:8080.

None of these is simply better. A separate program is easier to inspect and restart when something goes wrong. A single plugin is simpler to install and has fewer moving parts. Pick the trade-off you’d rather live with.

How they remember: summaries, techniques, or a memory store

This is where the three differ most, and it is the difference you’ll feel twenty hours into a playthrough.

Mantella uses summaries. “When a conversation ends, a summary of the conversation is saved to a local text file for each NPC in the conversation. These summaries are then loaded the next time an NPC is spoken with.” You can read and edit those files yourself, in My Games/Mantella/data/Skyrim/conversations/. That’s the same approach many AI games use — AI Dungeon’s Story Summary works the same way — and it has the same strength and weakness: simple and transparent, but a summary is only as good as what it chose to keep. Mantella’s own docs warn that “some smaller models may struggle to handle long term conversations and memory summarising.”

CHIM describes “long-term memory for in-game characters, employing various techniques to mitigate the lack of long-term memory in current LLMs,” alongside “dynamic character personalities that update over your playthrough.” Its public materials don’t detail the techniques, so we won’t guess at them.

SkyrimNet uses a memory store per character. “Each NPC has their own private memory store. Memories are written from that character’s first-person point of view and retrieved by meaning, not just keyword matching.” It adds two ideas that come straight from memory research: importance (“a memory of being attacked outweighs a memory of a passing pleasantry”) and decay (“memories fade over time at a rate proportional to how important they were”). NPCs can also write diary entries that become searchable memories, and facts bigger than one person — “A dragon attacked Helgen” — can be limited to the NPCs who would plausibly know them.

Those are the same designs academic work on AI characters is testing. MOOM builds a forgetting mechanism into long role-play memory, and DREAM organises a character’s memories as linked events. Our research index lists the rest. Whether any of it holds up over a full playthrough is exactly the kind of question the research says is hardest: long stories are where AI consistency breaks.

Mantella in Detail

Mantella is the most widely used of the three — its documentation cites “350k+ downloads” — and the best documented, so it’s the one most people start with.

What it does, in its own feature list: talk to “3,000+ NPCs, each with their own unique background”; NPCs “remember past conversations with you,” are “aware of in-game events” and “can see what you see”; they can “perform 20+ actions — follow, attack, trade, travel to locations, cast spells, and more”; they “can start conversations with each other, approach you, or join group conversations”; and it’s “fully playable in VR / SE / AE,” in “20+ languages.” It also runs in Fallout 4.

How to install Mantella

Mantella’s own quick start, condensed:

Install the required mods for your exact Skyrim version: SKSE (the VR version if you play VR), Address Library for SKSE Plugins, FonixData (for lip sync), UIExtensions (if you want to type instead of speak), SkyUI (for the settings menu), the Microsoft Visual C++ Redistributable, and Mantella itself.
Find your Mantella folder. In Mod Organizer 2, right-click Mantella and choose Open in Explorer. In Vortex, it’s Data\Mantella inside your Skyrim folder.
Create a free OpenRouter account, generate an API key under Settings → API Keys, and paste it into GPT_SECRET_KEY.txt in that folder.
Launch Skyrim through SKSE. Mantella opens its own window, which says “Waiting for player to select an NPC…” when it’s ready. Cast the Mantella spell on someone to start talking. Say or type “goodbye” to end the conversation.

Two warnings from the documentation are worth reading twice:

Match every required mod to your Skyrim version. The docs call this “the #1 reason for installation problems.” Check your version by right-clicking the Skyrim .exe and opening Properties → Details → File version.
Don’t keep Skyrim in Program Files. Mantella writes to the game folder, and “it is unlikely to work correctly if you have Skyrim stored in Program Files / (x86).” Move it somewhere like C:\Games\Steam.

What Mantella costs

Mantella itself is “free and open source.” The cost, if any, is the language model:

Free, through OpenRouter. The quick start sets you up with Gemma 4 26B A4B (free). Free models on services like OpenRouter come with usage limits; Mantella’s troubleshooting page lists “free requests have reached their daily / hourly / etc limit” as a cause of errors.
Free, on your own PC. Mantella connects to local model runners such as koboldcpp, and its docs suggest Gemma 4 E4B as a starting model. You need a capable GPU; see our local models guide for what your card can run, and our KoboldCpp setup guide for the runner itself.
Paid, through a model service. OpenAI, OpenRouter’s paid models, or any OpenAI-compatible API. You pay that service per use. Our OpenRouter roleplay guide covers how that billing works, and best LLM for roleplay covers which models are worth paying for.

As the docs put it: “No data leaves your PC unless you choose.”

Making Mantella respond in real time

Mantella is “configured to provide a balanced out-of-the-box experience,” not the fastest one. Its real-time guide lists fixes in order of impact:

Pick a fast model. Aim for “a response in less than 0.5 seconds”; the Mantella window logs how long each reply took. On OpenRouter, set Default Provider Sort to latency or throughput.
Set lip sync to “Lazy” — about half a second faster.
Enable Fast Response Mode — about another half second.
Tune the microphone. Lower the pause threshold, and turn on proactive transcription so your speech is transcribed while you’re still talking.

When Mantella isn’t working

From Mantella’s own troubleshooting page:

Symptom	Likely cause, per the docs
NPCs only say “I can’t find the right words at the moment.”	The model service is down, or the API key is missing or out of credit. Check `Documents/My Games/Mantella/logging.log`.
`Mantella.exe` closes immediately, or “cannot connect to port 4999”	Antivirus or firewall is blocking it. Allow `Mantella.exe` through both.
NPCs repeat the same line	Usually Skyrim is in Program Files. Move it.
Replies show in the Mantella window but aren’t spoken	Make a new save and reload it so the voice files register.
Mantella spells missing from inventory	An old version wasn’t fully removed. Follow the docs’ clean-upgrade steps.
NPCs describe their actions out loud	A smaller model isn’t following instructions. Try a larger one.
NPCs won’t follow, attack or trade	The action must be enabled in both the Mantella UI and the in-game menu. Or just say the action, e.g. “follow”.
Mic stuck on “Listening…”	Check the mic works elsewhere and is the default device. For non-English speech, switch from Moonshine to Whisper.
Skyrim crashes when an NPC starts speaking	A known clash with the Fuz Ro D’oh mod. Try disabling it.
`FileNotFoundError`	Mantella’s save data is on OneDrive. Point it at a local folder.

One more, for everyone this autumn: SKSE’s site carries a warning dated 14 August 2026 — “Bethesda has announced an incoming update to Skyrim. Please be prepared.” A game update breaks SKSE and every mod that depends on it until they are rebuilt for the new version. If all three mods stop working on the same day, that’s the likely reason.

CHIM

CHIM is the successor to Herika, the AI companion mod many players knew first; its repository calls itself the home of “the CHIM and Herika stack.” Development now happens under the Dwemer Dynamics organisation on GitHub, and the original HerikaServer repository points there.

What it offers, in its own words: “any NPC can be an AI, including group conversations”; “long-term memory for in-game characters”; “deep world awareness”; “an AI Narrator to narrate your adventures and provide help”; “function calling action commands (e.g., trade with me, move here, attack that monster, etc.)”; and “dynamic character personalities that update over your playthrough.” Its server connects to ChatGPT, koboldcpp, OpenRouter and several speech services. It is open source under GPL-3.0, and its Nexus Mods page is where players download it.

SkyrimNet

SkyrimNet is the newest of the three; its public repository dates from May 2025. Its pitch is simplicity and speed: one plugin, no separate programs, and “TTS starts speaking the first sentence while the model is still writing the second.”

Beyond the memory system above, three details stand out:

Different models for different jobs — “a fast, cheap model for action selection, a smarter model for dialogue.”
Realistic perception — “an NPC only reacts to what they could plausibly see or hear. People upstairs do not respond to conversations downstairs.”
Low system demand — its local text-to-speech “runs on the CPU; no GPU is required.”

It also ships “3,000+ pre-written NPC bios,” and generates one for any character without a bio. It is a free download from its GitHub releases page, and it supports Skyrim VR as well as SE and AE. Its public repository doesn’t state a licence, so don’t assume the code itself is open source.

Which One Should You Use?

You want to be talking to NPCs tonight with the least fuss: Mantella. The free OpenRouter quick start is four steps, and it’s the best documented.
You also play Fallout 4: Mantella, the only one of the three that covers it.
You care most about NPCs remembering you over a long playthrough: SkyrimNet’s memory system is the most detailed of the three on paper.
You want a narrator, or companions whose personalities change as you play: CHIM.
You play on Xbox or PlayStation: none of them will run. If you want AI characters on console, see our list of games with AI NPCs.

If You’d Rather the Whole Game Worked Like This

These mods put AI conversation into a world that was written for scripted dialogue — which is part of their charm, and part of their limit: the quests, the economy and the story still run on Bethesda’s rules. If you want a game where the narrator, the world and every character are AI from the start, that’s an AI RPG. Our benchmark scores 27 of them on seven axes from first-hand play, including the Memory & Continuity axis these mods are all trying to solve. And our NVIDIA ACE explainer covers how studios are building the same kind of character into commercial games.

Frequently Asked Questions

What is the best Skyrim AI NPC mod? The three most active in 2026 are Mantella, CHIM and SkyrimNet, and they suit different players. Mantella has the most documented setup, a free quick start and also covers Fallout 4. SkyrimNet runs entirely inside the game as a single plugin and has the most detailed per-character memory. CHIM, which grew out of the Herika companion mod, adds an AI narrator and personalities that change over a playthrough. We have not scored any of them.

Is Mantella free? Yes. Mantella is free and open source. Its quick start uses a free OpenRouter account and a free model, Gemma 4 26B A4B. You can also run a model on your own PC at no cost, or pay for a stronger model through OpenAI, OpenRouter or another compatible service, in which case you pay that service for what you use.

Does Mantella work on Xbox or PS5? No. Mantella, CHIM and SkyrimNet all require SKSE, the Skyrim Script Extender, which is only released for the PC versions of Skyrim on Steam, GOG and VR. Mantella’s documentation also requires Windows 10 or 11. None of these mods can run on Xbox or PlayStation.

How do I install Mantella for Skyrim? Install the required mods for your exact Skyrim version, including SKSE, Address Library, FonixData, SkyUI and the Mantella mod itself. Create a free OpenRouter account, generate an API key and paste it into the GPT_SECRET_KEY.txt file in your Mantella folder. Launch Skyrim through SKSE, wait for the Mantella window to say it is waiting for you to select an NPC, then cast the Mantella spell on a character. Keep Skyrim outside the Program Files folder.

Why is Mantella not working? The most common causes are installing the wrong version of a required mod for your Skyrim version, which Mantella’s documentation calls the number one installation problem; Skyrim installed in Program Files; antivirus or firewall blocking Mantella.exe; and an API key that is missing or out of credit, which makes NPCs reply that they cannot find the right words. A Skyrim update can also break SKSE mods until they are rebuilt.

Do Skyrim AI mods remember conversations? Yes, in different ways. Mantella saves a summary of each conversation to a text file for each NPC and loads it the next time you talk, and you can read and edit those files. SkyrimNet gives each NPC a private memory store written from their point of view, retrieved by meaning and fading over time by importance. CHIM describes long-term memory built with several techniques to work around the limits of language models.

Sources

Checked 26 September 2026. Mantella documentation (overview, Skyrim installation, issues Q&A, real-time NPCs) and repository; CHIM’s plugin and server repositories; SkyrimNet repository; SKSE.