Introducing Personica AI: A Cognitive NPC Brain for Unreal Engine

SwampRabbit_Labs
Tue, 06 Jan 2026 22:32:05 +0000
UE Marketplace

Product Website | Documentation | Community Discord

Hi everyone! I’m Chris from SwampRabbit Labs, and I just released Personica AI on Fab.

Personica is a C++ genAI Brain component for Unreal Engine focused on one goal:
using LLM language processing to analyze and update game worlds, not just generate dialog.

This project came out of my own frustration experimenting with generative AI in games, and in noticing that so many products are focused on generating assets or characters, not making the work of creatives and designers easier. Most solutions I tried were great at talking, but fell apart when it came to:

Updating character behavior beyond dialog

Turning what characters think into actions that characters do

Interpreting new events and information in the game world

Multiplayer safety and determinism

So I built Personica as a hybrid system:

LLM responses work alongside your traditional game design. Use as an all-in-one system, or modularly with your preferred AI kits.

Use generative AI’s inherent language processing to reason, think, and act.

A ranked memory system decides what NPCs remember (and forget)

Built-in LODs and request gating keep things performant and predictable

What Personica Is & Isn’t

Personica is:

A gameplay-first AI architecture that focuses on keeping the LLM in the background for seamless, dynamic gaming, instead of trying to show off new AI gimmicks.

A “referee” for games: an LLM suggests updates, but the Personica system lets game developers control what actually gets let through to the game world.

Designed for RPGs, sims, immersive worlds, and systemic NPCs.

Built to work with designers, writers, and existing AI systems.

Personica is not:

A replacement for writers or voice actors.

A “ChatGPT wrapper,” pure character generator, or text-only plugin.

A black box that takes control away from your game logic.

The AI doesn’t “run the game” or overwrite your carefully-crafted storylines.
Instead, it interprets, remembers, suggests, and triggers explicit gameplay actions you define.

For more information, check out the Documentation link above.

Use Case Examples

Guard NPC behavior evolves over time

A town guard becomes more suspicious and aggressive toward the player after repeated nighttime trespassing, even if the dialogue stays polite.

Faction trust changes without dialog

Helping a rival faction silently lowers an NPC merchant’s prices for allies and raises them for enemies, without the NPC ever explaining why.

Quest outcomes alter NPC personality

Sparing an enemy causes them to become fearful and evasive later, while killing their ally makes them hostile on sight.

International relations analysis in Grand Strategies

After repeated border skirmishes and broken treaties, Personica mutates the diplomatic “Trust” state between two nations, causing future negotiations to start hostile even if the player offers generous terms.

Game systems that learn from previous events

The game world’s governing council “remembers” which policies historically stabilized the economy and begins favoring similar decisions autonomously.

NPC memory affects future gameplay options

An NPC refuses to help open a locked gate because they remember you previously betraying them during a side quest.

Dynamic quest gating without branching trees

A quest becomes unavailable because the NPC’s trust never reached the required threshold, not because the player chose a “wrong” option.

“But I can do all that already without Personica!”

Yes, and you should continue to! Personica is designed to work alongside hand-scripted game design, not replace it completely. The plugin can take over for the tedious algorithm and branching construction required in traditional game design. Focus your time and energy on building the main storylines, tense actions points, and key systems, and spend less time tweaking algorithms and trigger rules for minor functionality that a player may never see.

Building a complex game world requires both wide and deep design. Personica takes over the “width” of game design so you can focus on the “depth.”

An example of an prompt that is sent to an LLM mid-conversation, with trait updates, conversation history, and memory system. Profiles and prompts can be customized to include more or less information.

Current State

v0.9.3 is live on Fab

Free downloadable demos showing dialog + utility actions using a local LLM is available for download

Designed to be extensible and modular (use only what parts of Personica you need)

My goal right now is real-world feedback from Unreal developers to ensure that I am building LLM tools that are useful, practical, and scalable.

I’m very open to feedback, positive or critical, and happy to answer technical questions about how the system works!

Thanks for taking a look,
Chris
SwampRabbit Labs

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