Secrets are currency, depending on how much value is placed on keeping it a secret. Perhaps she asks for favors.

Hmm. That could work. Not in a direct sense (ie "Do this thing for me or I tell") as that seems a little too "human" but maybe knowing a secret about a being gives her a measure of power over them in a literal sense. Most beings don't like that, so they are often willing to trade with her, (possibly favors, possibly other secrets) at which point she gives the secret back to them by plucking it out of her head (it's fairy magic, it should be a little weird) and handing it to them.

Going further (and I'll have to talk to the Warlock's player about incorporating this into her Pact) maybe she does the reverse as well: having mortals tell her their own secrets in exchange for favors/boons from her. I could very easily see part of the Warlock sealing her Pact with Mavalene involving her telling the fairy her own deepest secret.

That definitely got the gears turning. Thanks!

Or she could be a secret vault, where you have an important secret that is too dangerous to keep. I doubt a Fae would allow herself to be used for human schemes without a good return, but imagine a spy having to transport a secret and being able to leave it with her and then getting it back when they've reached safety.

That's a cool idea as well. Might be an interesting plot hook for an adventure where someone seeks the Warlock out in order to get an audience with her patron for such purposes.

So talked to the Warlock player about the deepest secret being part of the Pact and asked if her character agreed to share the secret with Mavalene (in which case they both know it) or if she gave it to her (in which case it would have been plucked out of her head and the Warlock no longer remembers.) She chose the latter, so this should be fun.

The player also made clear that the Warlock learned her lesson with the "giving" and now is sure to share the secrets she comes across instead of giving them.

Cool! The plot possibilities when dealing with the tricksy folk are endless.

Finally had our first in-person session last night. It was great actually getting people around a table and rolling real dice. Just need to get back in the facespace DMing groove again. 7 years of Roll20 has spoiled me from having everything a simple click away and it doing the math for me.

Sounds like fun.

My players instantly loved one of the NPCs I introduced (a dim-witted but good-hearted Dragonborn war priest) to the point one of them was contemplating buying and painting a mini for him since I didn't have one.

So of course he got killed by the orcs they were fighting 15 minutes later.