So in my game the past two weeks, the party has interrogated four people with the spell. Three were prisoners they intended to execute after they got information, one was an ally they were suspicious of. The prisoners had been involved in poisoning a town.
One of the prisoners managed to save herself by being straightforward and honest, explaining that she was forced to work against her will by a geas. That seems like a ridiculous lie, but she was in a zone of truth so they believed her. (I'm setting up an enchanter villain who tortures his enemies by compelling them to undertake horrific acts.) She gets to live.
Another prisoner was asked his loyalties, and he realized they wanted information about his mission, so he clammed up. They explained that if he was also being geased they might let him live. He said he didn't think he deserved to die for following orders. They asked straight up, did you have any qualms about poisoning the town? He was quiet for a moment, struggling, but then shrugged and smiled and said, no. He was glad to do it. Execution time!
Third prisoner, seeing what's happened, says that he's killed lots of people for his country, and while he didn't feel it was right to murder people outside of combat, he knew he had to follow orders or he'd be killed. They asked if he would help them instead of the person who gave him orders, and he said yes, and that he'd rather betray his master than die right now. They ask him a few more questions about whether he intends or is thinking of betraying the PCs, and he says no. His life is spared, for now.
Then there's the suspicious ally. That ally has been giving the PCs advice on their missions because she has lots of magical knowledge of events in the wider world, and they're suspicious of how she knows all those things. The ally controls a library with tons of obscure knowledge, and she has magic that lets her enter books and see events in the book as if she were there. (The party has abused this by storing prisoners in books.) So a PC gets her into a zone of truth and straight up asks her, are we in a book?
The answer is, well, yeah. For reasons that are complicated*, the party consists of people in a history book, and the NPC is trying to get them to do things differently so that she can learn how to deal with a threat in the present day. But she figures if the PCs know they're not real, they'll not be useful anymore because what motivation would they have to do anything? So, since she's a master of language, she verves and redirects and selectively interprets their questions to basically tell the PC an answer that she can justify as being "not false," even though it is totally deceptive.
One of my players clued into that, but figured his 8 Intelligence PC wouldn't realize he'd been tricked. After the game he told me he was totally pissed that I'd cheated. Hence this thread.
*Reasons:
[sblock]A demon lord gets loose and destroys most of civilization. A handful of survivors who hope to defeat the demon lord include this NPC, who is a librarian and wizard, and who knows a spell that lets you hop into a book. But normally the book is just static; it's more like "use a book as a focus to create a pocket dimension based on whatever is on that particular page." However, the survivors found the First Book, written by the creator god himself, which starts with the words, "We create the world."
With some magic shenanigans they managed to splice a history book into the First Book, so now that history book is basically alive, not static. The NPC librarian goes into the book and nudges some events to try to find critical information from the time before the demon lord is released. Her intention is to find this information then get out of the book, which would strand the PCs in a sort of fake reality that would eventually be destroyed by the book's version of the demon lord.
Yes, it's sort of Inception-y.
What I have planned, though, is for the party to find a way to drive away the demon lord for a time -- but that method won't work in the real world. So the NPC librarian will stick with the party, trying to find a more permanent solution. Eventually they'll come upon a mage who actually can create physical objects out of words, which would allow the PCs to at least get out of the book they're in, and into the real (demon-lord-apocalypse) world. Then if they can find the original creator god and get his help, they can have him make the reality from the book they came from be the Real Reality. They can save their world and be real.[/sblock]