D&D 5E Mysteries, Zone of Truth, and Savvy Players?

If I were a player in that adventure, I supposedly agreed that we're interested in discovering the mystery the hard way, so I would not play a PC capable of spoiling it all with a click, or I would pretend to forget I could click that button.

I think this is also a fair point. You either run with it and design the mystery around the spell, or you agree not to allow the spell.

When I started my pirate campaign, I agreed with my players that they would not choose any race that could naturally breath underwater, or use flying spells. I explained to them that the campaign was meant to revolve around the threat of water and I didn't want that threat diminished so easily. I wanted them to do a lot of sailing, and to deal with water in some manner, by using what the game had to offer. Spells that provided underwater breathing however, or shape shifting into a shark, were perfectly fine.

I think it can work fine if you can get your players on board with such an idea.

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One of the players previously cast detect magic and viewed all the NPCs – who would soon become suspects – and I didn't describe any of them as radiating enchantment magic, so that rules out geas.

Does detect magic note that some being is under a Geas? The Geas might only show up when active imho, as long as the trigger for it does not occur there should be no detecting.

And in the case the zone of truth is up the player will show as being under a magic effect anyway, namely the zone.


We've started a new campaign, and after their first session my players are set up to investigate a mystery of a stolen auction item. My group is comprised of experienced, clever, genre-savvy players, and everyone has some DMing experience. They're a joy to DM for but also a challenge! B-)

One of the players has access to the zone of truth spell, and he has the authority/permission to use that spell on multiple suspects (provided it's limited to questions pertaining to the investigation). I thought I had the mystery well designed so that zone of truth wouldn't break it, but now that I have more time to reflect on my players' skill level, I may need to think this through more.

In the past, when I've run a mystery for other less experienced players, I was able to use evasive answers and counter-questioning to trip them up with zone of truth. I even managed to confound one experienced player during his first casting of zone of truth (the questioned killer had given the familiar of a spellcaster poison to sprinkle in the drinks of the murdered, claiming it was tea). Those tricks worked because of lack of experience – either generally or with the spell. However, these players are far too experienced to be tripped up so easily.

EDIT: For instance, I'm fully expecting "answer in yes/no format only" or "repeat after me" strategies.

Have you successfully run a mystery for experienced genre-savvy players? How did you handle intelligent questioning via zone of truth?

Ah now I get it what you have to do, it is a pretty mundane solution and only requires you to alter some of the NPCs agendas so slightly:

Make it, that if the NPC who got clues is questioned with zone of truth really gives out some info (the least info possible though) - but the caster of the zone of truth gets the indication the player is lying. Why so? Because he has got something to hide in connection with the missing item. Maybe he is involved its disappearance, maybe he has something else to hide. Maybe he did use the item without being allowed to, maybe he intended to steal it, maybe he intends to buy it from the thieves, maybe he knows something extreme about the item (e.g. the item is in fact a very powerful artifact or a doomsday device)

I like it! False positives and multiple suspects. That is also a very good thing to throw in. Npc's may be lying for a different reason unknown to the players.


Mod Squad
Staff member
One of the players has access to the zone of truth spell, and he has the authority/permission to use that spell on multiple suspects (provided it's limited to questions pertaining to the investigation).

Who gave them permission? Are there witnesses to the questioning other than the PCs? Are there advocates for those under investigation to protect them against predatory questioning?

Also, the spell notes that the casterr knows if the subject made of failed its save. Note that nobody else does. The situation becomes complicated if anyone has reason to doubt the PC, who is the only ones around with the spell....

EDIT: For instance, I'm fully expecting "answer in yes/no format only" or "repeat after me" strategies.

Yes/no, without qualification, can be massively abusive. "Have you stopped beating your wife?" and the like.

Even Yes/No can be up to interpretation - "Did you see Joe last night?" Well, the subject and Joe talked in a back alleyway, and it was very dark. strictly speaking, the subject can say they didn't see Joe, in that they could not be sure, by visual identification, that it was Joe. Or, alternatively, the subject saw someone in the dim lighting that was Joe's general size, and sounded like Joe, so the subject honestly thinks they saw Joe, when they did not. Since "Maybe" is not an option, the party may get an inaccurate impression of events.

So, mislead them with those Yes and No, and make them weed through the complication. Make it so two people answer they saw Jae, and their answers are mutually exclusive.

Also, note that Zone of Truth has a duration of 10 minutes. Run a timer.

Alternatively - this is a thing I've learned running Ashen Stars (a game largely about mysteries) - make it so the tricky bit isn't getting information, but in figuring out what the information means.

Make it so the mystery they are investigating is not the only thing going on that people might want to hide, and the PCs have to weed through them. Yes, Joe was there that night... but he was visiting his mistress, and his presence has nothing at all to do with the crime under investigation.
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It depends on your goal as the DM. In general, my strategy is to give evasive answers in such a way that a savvy player can pick up on the evasion for follow up questions. There are a handful of exceptions, such as if revealing information would spoil the adventure, but in general I try to avoid this when possible.

I'll admit I hate the fact that the caster knows if the spell works or not. If it compelled answers to those who fail, without letting the caster know who failed, the players have to decide if the answers are useful or not. As it is, violence is the fallback for many players if the NPC makes the save.


Ok, I'm going to say run with it.

Zone of Truth actually works. It easily reveals the mystery.

But, remember that bit about only asking questions about the problem? It also uncovers something else horrible.


Another approach.

Zone of Truth requires that the subject be free to choose their own words. If you force them to quote you/repeat after you, or say "yes/no", Zone of Truth doesn't work right. If they choose to use those words, then it works.

The external coercion warps the intention of the subject.

And if you cut them off, you get the Truth of what they intended to say, not what they said. So if you ask "Did you kill her?" and they say "No, I [...]" and you cut them off, you get "Truth" because the rest of the sentence was "No, I am not going to say I killed her. I am not the type to kill people for no reason."

This means Zone of Truth can be defeated by being silent, or blathering on forever.


Or mix these two. Onion adventure.

Layer 1 is the auction.
Layer 2 is the theft and investigation
Layer 3 is something discovered during the investigation


Mod Squad
Staff member
but the caster of the zone of truth gets the indication the player is lying.

That's not how the spell works (in 5e, at least). The spell does nto pick out falsehoods. The caster knows whether the save was made, and if it was failed, the subject is incapable of telling deliberate falsehood. Basically, everything in the failed save must be true.

In 3e: "Creatures within the emanation area (or those who enter it) can’t speak any deliberate and intentional lies. Each potentially affected creature is allowed a save to avoid the effects when the spell is cast or when the creature first enters the emanation area. Affected creatures are aware of this enchantment. Therefore, they may avoid answering questions to which they would normally respond with a lie, or they may be evasive as long as they remain within the boundaries of the truth. Creatures who leave the area are free to speak as they choose."

In 5e: "You create a magical zone that guards against deception in a 15-foot-radius sphere centered on a point of your choice within range. Until the spell ends, a creature that enters the spell’s area for the first time on a turn or starts its turn there must make a Charisma saving throw. On a failed save, a creature can’t speak a deliberate lie while in the radius. You know whether each creature succeeds or fails on its saving throw. An affected creature is aware of the spell and can thus avoid answering questions to which it would normally respond with a lie. Such a creature can be evasive in its answers as long as it remains within the boundaries of the truth."

So this basically leaves npc's wide open to trying to avoid answering the question, or giving answers to things that weren't asked, as long as they speak the truth. They can even just try to fill the 10 minutes with nonsense.

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