This one is more of a one-page component of an adventure than the adventure itself. This is an answer to the issue of PCs finding information. Sometimes, it’s just as easy to hand it over—have one of the PCs with the proper build know the information. Sometimes, it can be fun to breakdown how and where they get that information. For me, when it comes to ancient or otherwise forgotten knowledge, I force them to do what I did for so much of my time in university: do a little research!
Story
In search of forgotten or obscure knowledge, the PCs seek out an archive that they know to have ancient sources—tomes and scrolls and maybe cuneiform tablets. The knowledge of which archive to visit and where that archive can be found might be it’s own little adventure following a similar path.
Places
The Town: This was once the main city of the state, but with changes in dynasties and power centres, its importance has dwindled and so too has its population. It is now peripheral to politics, but still has the memories of that all-but-forgotten time—especially in its archives.
The Archives: This might be a state institution still as it was when it was first created, or maybe it fell into private hands after power moved away. It fills a tower near the centre of the city, with its collection reaching through three underground levels.
People
The Curator: The archive—whether it is in private or public hands—will have a managing and/or controlling figure. They will be the one whom the PCs will need to convince to provide them access if not assistance in their quest. As this is a kind of librarian, I would argue they will be enthusiastic, generous, and helpful. In my version, they are thrilled someone wants to use the archive to expand their knowledge, and will be a useful ally in the search.
The Troll: Not a literal one, but someone seeking power and trying to protect theirs. That’s this person. They see the PCs efforts to uncover knowledge as reducing their own power—forgetting that knowledge is not a zero-sum game. They will do their utmost to create obstacles for the PCs, though they will not do so overtly. The Troll can be an outside figure who hasn’t cared about the archives until somebody wants to use it.
Events
The Approach: The PCs will need to introduce themselves to the Curator and gain permission to access the archives. They may not be able to explain fully what they want if their purpose is to remain secret, but they’ll need to gain the Curator’s trust and acceptance if not their cooperation.
The Search: There can be many layers to the Search. The Curator will understand the structure of the archive and will have some form of indexing, but even then, the PCs will need to go through different works seeking for clues. Those clues will lead to other documents with more clues. If the players are reacting negatively to this scenario, let the PCs quickly hit upon the information they need. If the players are engaged in the pursuit, there are multiple nuggets of information in different sources that all lead to the final accumulation of the knowledge the PCs seek.