The PCs have decided, wisely, to take advantage of a DF Felltower institution: sages.
Like in old-school AD&D gaming, you can find out things by experiencing them or asking NPCs.
The PCs want to hire a sage.
There are a few issues, though.
One is the group makeup, again, has become very much crusading religious fanatics and would-be fanatics (Ulf, Heyden, Aldwyn, Sir Bunny, etc.) buttressed by a small squad of misanthropes (Galen, Bruce, Gerry, etc.)
So who can go and find and hire a sage? Not the misanthropes. Some of them live in the wilderness, and others are just completely awful at finding someone and getting them to react well to them. The fanatics, well, no so much either. Ulf is likeable, but has Paranoia. Wyatt isn't around to do it (I don't allow PCs who missed sessions to jump in between sessions to execute prep. It keeps you from having a stable of utility guys who help out even if you don't run them often.) The others generally aren't that smart and they need Research or IQ rolls to find a sage with Hidden Lore (Lost Civilizations) to answer their questions.
So it's a bit of tricky situation. The ones with good base rolls have penalties to bring it down. Those with poor base rolls have poor rolls and many of them also have penalties to bring it down.
How do you bring it up?
You spend extra money, of course, per "Where Did You Find This Guy? on DF15, p. 29. I'm not even at any of my PCs as I type this, but I know the page offhand, which is a measure of how often I have to tell people to go read it.
Once that's done, of course, it's just a matter of money and questions. I did caution them that they can get specific, and get specific answers, but the sage won't through in general-but-important information.
Hopefully they'll figure it out . . . but the tendency to go for debilitating social disadvantages to bulk out your disad pool, and that of several players to get more of such by cheaping out on Resurrection costs, means it's getting harder to find reasonable beings to help them out.