Tusk's Vault is an AI chatbot built directly into your Foundry game as a module. Installing it gives you a "lite" version of the full experience, which runs inside the module on its own.
You'll want a Gemini API key for the good version of this. Go to Google AI Studio, make one, and either leave it unbilled if you're unsure or set yourself a spending cap. Without a key it still works, it just quotes the matching passages back at you instead of writing you an answer.
Tusk grounds itself in the lore you provide. In the lite version that's a journal folder called Tusk's Lore. Put your notes in there and Tusk becomes an expert on them, answering questions from you and your table in chat, digging out what happened three sessions ago and pointing you at the entry it came from. If you're a GM sitting on a lot of lore, this might be the module for you, since both you and your players can ask and get answers.
It won't make anything up. Ask about something your notes don't cover and it tells you it doesn't know, rather than inventing a nice-sounding answer you then have to live with. You still do the worldbuilding. Tusk just remembers what you came up with.
It isn't a stiff lookup tool either. You can ask it all sorts, it handles a wide range of topics, and it'll happily settle an argument between two players about what the duke actually said back in session four. Serious questions or silly ones, the answer comes back in chat. It won't get squeamish, either. Campaign notes get dark, and a chatbot that refuses to discuss the murder your party committed is no use to anyone.
In the settings you decide who can use it and how it replies: everyone at the table or GMs only, plus named exceptions for anyone in between, and whether answers are whispered to whoever asked, whispered to you, or posted publicly. It also respects Foundry's own journal permissions, so players never get answers out of notes they can't read.
Lite reads one folder, and only as much as fits into a single question. Fine for a young campaign, not enough for years of notes. That's what the full version is for: a free, open-source app you run on your own machine that reads the notes you already keep, whether that's Word documents, PDFs or a whole Obsidian vault, runs on whichever model you fancy, and keeps your API key out of the browser entirely. Try Lite first and see if you get on with it.
kochitusker.github.io/Tusks-Vault
Foundry v13 or newer, verified on v14, and a GM needs to be online. MIT licensed, source on GitHub.