Zone of Truth - Question

[Tawmis]

The spell is as follows:



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 creatures can be evasive in its answers as long as it remains within the boundaries of the truth.


Because it's a radius spell, if the caster is in that radius it impacts them as well.

So here's the question.

A demon is bound. Paladin casts Zone of Truth on it. Paladin is in the sphere too, because he's also holding the demon.

According to what I read, the spell impacts the caster.

So now - during the exchange - the demon asks the Paladin, "Does anyone in your party plan to kill me?"

(Which the Paladin knew they were going to do)

Paladin had failed his CHR Save.

Which means he can't lie/deceive to the demon.

Would you agree?

[Unoriginal]

The spell is as follows:



Because it's a radius spell, if the caster is in that radius it impacts them as well.

So here's the question.

A demon is bound. Paladin casts Zone of Truth on it. Paladin is in the sphere too, because he's also holding the demon.

According to what I read, the spell impacts the caster.

So now - during the exchange - the demon asks the Paladin, "Does anyone in your party plan to kill me?"

(Which the Paladin knew they were going to do)

Paladin had failed his CHR Save.

Which means he can't lie/deceive to the demon.

Would you agree?

Sure, the Paladin is affected.

Don't know how it changes anything, though. Paladin can just say "yes" and if asked "who" they can answer "I'm a Paladin and you're a Demon. Do the math."

Or, given that the Paladin is forcibly maintaining the Demon in a truth spell, the Paladin could just not answer the question. Or just say "I'm Paladin, planning to kill Demons is part of the duties".

[Keravath]

I think you should keep in mind that a saving throw is rolled every 6 seconds at the start of their turn.

"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."

Paladins typically have pretty good saving throws with high charisma so all he has to do is have a long winded answer that lasts until he passes, at which point he says "No" assuming the answer matters for some reason ... or just tell the demon "Yes" or say whatever they would normally say if they don't care whether the demon learns the truth.

[Unoriginal]

I think you should keep in mind that a saving throw is rolled every 6 seconds at the start of their turn.

"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."

Paladins typically have pretty good saving throws with high charisma so all he has to do is have a long winded answer that lasts until he passes, at which point he says "No" assuming the answer matters for some reason ... or just tell the demon "Yes" or say whatever they would normally say if they don't care whether the demon learns the truth.

Also the Demon doesn't know if the Paladin has failed the save or not.

[Zhorn]

I think you should keep in mind that a saving throw is rolled every 6 seconds at the start of their turn.

"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."

Paladins typically have pretty good saving throws with high charisma so all he has to do is have a long winded answer that lasts until he passes, at which point he says "No"
Is that how it is meant to work? that doesn't sound right.
I thought once you failed the save, you were under the effects of the spell for the duration so long as you remained in the zone, no repeat saves.

[stoutstien]

The spell is as follows:



Because it's a radius spell, if the caster is in that radius it impacts them as well.

So here's the question.

A demon is bound. Paladin casts Zone of Truth on it. Paladin is in the sphere too, because he's also holding the demon.

According to what I read, the spell impacts the caster.

So now - during the exchange - the demon asks the Paladin, "Does anyone in your party plan to kill me?"

(Which the Paladin knew they were going to do)

Paladin had failed his CHR Save.

Which means he can't lie/deceive to the demon.

Would you agree?

What plan of existence is the bound demon on? Kill and sending it back to native plains aren't necessarily synonymous.

[Hytheter]

Zone of Truth doesn't even compel an answer, so the paladin can just remain silent, or remind the demon who's asking the questions here.

Besides, even if the paladin is literally standing next to the demon (such as by holding them) it should be trivial to cast the spell such that its radius contains the demon but not himself.

[Lunali]

Is that how it is meant to work? that doesn't sound right.
I thought once you failed the save, you were under the effects of the spell for the duration so long as you remained in the zone, no repeat saves.

The wording is unclear, the save is rolled every 6 seconds whether you've passed or failed previously. If you fail, you can't lie, but there's nothing saying that if you succeed that you can now lie again.

[Zhorn]

The wording is unclear, the save is rolled every 6 seconds whether you've passed or failed previously. If you fail, you can't lie, but there's nothing saying that if you succeed that you can now lie again.
It's just in regards to Keravath's comment in post #3, suggesting that the truth effect is something you can time out in a single round which to me doesn't sound right.
That reading is the first time I've heard that interpretation.

Looking into the question of how many rolls, I was able to find


https://twitter.com/JeremyECrawford/status/974021510108082176
Q: How does Zone of Truth work exactly? It seems the saving throw repeats until you're going to fail. But then does it keep repeating once under the spell? If not, why make a saving throw in the first place, it seems it'd be simpler for it to just work.
A: Zone of truth requires you to make a saving throw when you enter the zone for the first time on a turn or start your turn there. If you fail your save against the spell, you don't keep making the saving throw; you're now affected by the spell for its duration.
Which was more to my understanding and previous observed rulings on how other tables I've seen have ran it.

Saving against every 6 second, I can see that reading; though is sounds a bit cheesy to do the whole 'keep making this throw' song and dance. I won't say that part is wrong, just that it reeks too much of that tactic some DMs do where they keep telling you to reroll till you fail (or conversely a plot important roll that they keep saying 'roll again' till you succeed).
Roll once, that result sticks until there is a change in the situation. <- Editor's note: this comment is in regards to DMs fishing for failures/successes when asking for immediate repeat rolls. This is not meant to be a ruling about the subsequent saving throws on different rounds for Zone of Truth, just a comment of what it reminds me of, and I communicated that poorly.

[Lord Vukodlak]

The wording is unclear, the save is rolled every 6 seconds whether you've passed or failed previously. If you fail, you can't lie, but there's nothing saying that if you succeed that you can now lie again.
According to Sage Advice once you fail the save youÂ’re affected for the duration.

[Lunali]

Saving against every 6 second, I can see that reading; though is sounds a bit cheesy to do the whole 'keep making this throw' song and dance. I won't say that part is wrong, just that it reeks too much of that tactic some DMs do where they keep telling you to reroll till you fail (or conversely a plot important roll that they keep saying 'roll again' till you succeed).
Roll once, that result sticks until there is a change in the situation.

If you do go with that interpretation, it means the caster just keeps asking the same question until the intended target answers with a failed save.

Personally, I run with a more fun (for me) interpretation where you roll after making the false statement, if you fail, you say the truth instead.

[HolyDraconus]

we ditched this spell for a previous edition version of it. This edition it flat out does not work as intended. Sure, you as the caster know if someone fails, but NOTHING about the spell compels you to speak. So beat the save, you can lie if you want but the caster only knows that you didn't fail the save; no idea if what is being said is true or false. Fail the save, the caster knows you failed, so you simply shut up if you don't want to tell the truth. Or you can lie while under the effects of it: Modify Memory forces the clause of willing to pop up, cause if you think its true, even if its a lie, doesn't ping on the zone as a lie and thus preventing you from saying it. Its just a bully spell that doesn't work anymore.

[Unoriginal]

we ditched this spell for a previous edition version of it. This edition it flat out does not work as intended. Sure, you as the caster know if someone fails, but NOTHING about the spell compels you to speak.

And?




So beat the save, you can lie if you want


No you can't.


but the caster only knows that you didn't fail the save; no idea if what is being said is true or false.

If the save is failed you can't say anything but the truth. What you believes to be the truth, at least.


Fail the save, the caster knows you failed, so you simply shut up if you don't want to tell the truth.

Again, and?



Or you can lie while under the effects of it: Modify Memory forces the clause of willing to pop up, cause if you think its true, even if its a lie, doesn't ping on the zone as a lie and thus preventing you from saying it. Its just a bully spell that doesn't work anymore.

You can't lie under the effect of Zone of Truth. If you want to say stuff that you know aren't true while under it, you need to mess yourself up until you believe it's true.

[MoiMagnus]

Zone of Truth prevent lies, and doesn't comply peoples to actually say anything. So assuming a failed save, the Paladin cannot say "no", but is not forced to actually answer.

[Which is probably for the best. The existence Zone of Truth already makes tribunals and justice system degenerated enough (in the meaning of "wildly different from real life"), if Zone of Truth was actually effective at obtaining detailed truth, that would be very annoying for world-building. That's only a 2nd level spell for Bards, Cleric and Paladin, so quite common.]

Though, even out of Zone of Truth, why would he Paladin ever answer this question? I'd probably answer "I'm not here to answer questions, I'm here to ask some, so tell me, [question]?".

Unless you're not in position of power, and need the Demon's cooperation. But I don't see why the Demon will actually trust the Paladin, unless the Paladin's vows actually include to keep your promises (even those made to Demons). In which case the Paladin would actually be bound by his answer, even if there was no Zone of Truth.

[Sigreid]

The defense against zone of truth is to no answer any questions.

[Unoriginal]

Zone of Truth prevent lies, and doesn't comply peoples to actually say anything. So assuming a failed save, the Paladin cannot say "no", but is not forced to actually answer.

[Which is probably for the best. The existence Zone of Truth already makes tribunals and justice system degenerated enough (in the meaning of "wildly different from real life"), if Zone of Truth was actually effective at obtaining detailed truth, that would be very annoying for world-building. That's only a 2nd level spell for Bards, Cleric and Paladin, so quite common.]

Though, even out of Zone of Truth, why would he Paladin ever answer this question? I'd probably answer "I'm not here to answer questions, I'm here to ask some, so tell me, [question]?".

Unless you're not in position of power, and need the Demon's cooperation. But I don't see why the Demon will actually trust the Paladin, unless the Paladin's vows actually include to keep your promises (even those made to Demons). In which case the Paladin would actually be bound by his answer, even if there was no Zone of Truth.

Also a Demon would need to be singularly out of it to not know the answer is "yes" by default. I mean they're a Demon.

Plus again the Demon won't know the Paladin succeeded or not.


The defense against zone of truth is to no answer any questions.

Though in some cases it doesn't work.


"Are you the one who killed the princess?"

"..."

"That silence's pretty damning, you know? Well, less damning than murder but still."

Best defense against Zone of Truth is something true but misleading, and interrogators who are too confident in their capacities.

[Segev]

Why would the demon ask that, and why would the paladin lie about it, anyway?

[JackPhoenix]

we ditched this spell for a previous edition version of it.

Which previous edition? Because 3.5 version is *worse*: it allows only one save, and doesn't tell the caster if the target succeeded or not. Otherwise, it works exactly the same: the target knows he can't lie and doesn't have to answer. 4e rituals equivalent to it are even worse: they simply give the caster a bonus on Insight checks.


This edition it flat out does not work as intended. Sure, you as the caster know if someone fails, but NOTHING about the spell compels you to speak. So beat the save, you can lie if you want but the caster only knows that you didn't fail the save; no idea if what is being said is true or false. Fail the save, the caster knows you failed, so you simply shut up if you don't want to tell the truth.

So, exactly like 3.5, except the caster knows if you've failed the save or not.


Or you can lie while under the effects of it: Modify Memory forces the clause of willing to pop up, cause if you think its true, even if its a lie, doesn't ping on the zone as a lie and thus preventing you from saying it. Its just a bully spell that doesn't work anymore.

So, again, just like in 3.5. You can't lie in it, but the spell never revealed if what you believe is the truth actually is.

[HolyDraconus]

the spell that my group switched this with was Adnd's Detect Lie. Mainly cause it doesn't have a loophole baked in about willing lies, outside of using the spell in Reverse, and even outlines that.

[Sigreid]

If you say something that isn't true, that you believe to be true; you didn't like, you were just wrong.

Seen too many people recently that accuse others of lying when they were just wrong.

[Unoriginal]

you can not tell a WILLING lie. I even mentioned Modify Memory, but you don't even need to go that far and involve magic TO lie in it. Let me try again to explain cause I think some of you aren't understanding what I am saying, by using an example.


Paladin asks the Demon who told you to kill the villagers. The entity that tells the Demon to do the deed says its the Paladin's mother. So the Demon replies "your mom". If the mother summoned the Demon, then in that way that statement is true. Otherwise, its a lie. Zone of Truth does not care about anything other than the perception of those that are speaking, in concerns of truth or falsehood. In the scenario I gave, your mom should be the truth ONLY if the Demon was summoned: it was not summoned. But going off its own knowledge, it responds with your mom is the truth. Though its a lie. In the Zone of Truth. AFTER it failed the Save.

It's not a lie if the person believes it. It can be false, but not a lie.



But that's a bit specific so lets go deeper. Paladin asks Rogue what color is the sky. Rogue says Red. SAYS Red. Its still the Truth, since the Paladin never specified WHICH sky, so that bypasses Zone of Truth.

That is a badly worded question to find out the truth, however language does contain context.

If the Rogue says the sky is red, then the Paladin can ask "the sky of the world we currently are on?"



Are you seeing the issue yet? ZoT has a heavy reliance of perception to discern what is truth or not

All truth is a question of perception.



and without BEING the person asking AND answering the questions, in effect interrogating yourself, it at the most basic level can not help you learn the truth.

Zone of Truth is to make so there is no lie spoken, not to extract the truth.



And the spell that my group switched this with was Adnd's Detect Lie. Mainly cause it doesn't have a loophole baked in about willing lies, outside of using the spell in Reverse, and even outlines that.

Does AD&D's Detect Lies somehow detect when someone says something false they honestly believe is the truth?

[MoiMagnus]

Does AD&D's Detect Lies somehow detect when someone says something false they honestly believe is the truth?

From some random online source, the AD&D2 spell I've found is
"A priest who casts [detect lie] is immediately able to determine if the subject creature deliberately and knowingly speaks a lie. It does not reveal the truth, uncover unintentional inaccuracies, or necessarily reveal evasions. The subject receives a saving throw vs. spell, which is adjusted only by the Wisdom of the caster."

It doesn't looks different from 5e's version to me, but I might not be good enough at exploiting bad wording.

[Sigreid]

Almost looks like some people are going for the Oracle of Delphi thing. She wasn't really supposed to be a prophet, she spoke the truth, whether she knew what it was or not.

That would be a cool divination spell, but for 8th or 9th spell level.

[Reynaert]

If you're in a zone of truth, what prevents you from mentally asking yourself a different question, and then answering that question aloud? Or even just saying something that just isn't the answer to an asked question.

"I didn't say the sky was red. I just said the word 'red' a short while after you warbled something about the colour of the sky, which I chose to ignore."

Basically, the only think ZoT is good for is for a willing person to prove their innocence. Let the cleric cast it, they willingly fail the save and then speak a full, detailed and specific sentence that they did not do whatever they were accused of.

In fact, if I ran a judicial system and had Zone of Truth at my disposal, that would make it very easy to work around the whole issue. Just make the rule "you're guilty until proven innocent by stating in full detail that you are innocent in a zone of truth, for which you willingly fail the save". Easy peasy. (Except if the caster is corrupt and lies about the accused having willingly failed their save, which is sorta why civilized societies have 'innocent until proven guilty' as the bedrock of their judicial system).

[stoutstien]

If you're in a zone of truth, what prevents you from mentally asking yourself a different question, and then answering that question aloud? Or even just saying something that just isn't the answer to an asked question.

"I didn't say the sky was red. I just said the word 'red' a short while after you warbled something about the colour of the sky, which I chose to ignore."

Basically, the only think ZoT is good for is for a willing person to prove their innocence. Let the cleric cast it, they willingly fail the save and then speak a full, detailed and specific sentence that they did not do whatever they were accused of.

In fact, if I ran a judicial system and had Zone of Truth at my disposal, that would make it very easy to work around the whole issue. Just make the rule "you're guilty until proven innocent by stating in full detail that you are innocent in a zone of truth, for which you willingly fail the save". Easy peasy. (Except if the caster is corrupt and lies about the accused having willingly failed their save, which is sorta why civilized societies have 'innocent until proven guilty' as the bedrock of their judicial system).

in a world where zone of Truth is a reality so are numerous magical effects and spells that can literally alter somebody's memory and perception of Truth. there's also a handful of class abilities that allow you to flat out bypass ZoT. It's basically the d&d version of the polygraph test.

[Sigreid]

It could be used in a situation where refusing to answer the question asked is seen as a defacto admission of guilt with all the consequences that go with it.

[Tawmis]

Why would the demon ask that, and why would the paladin lie about it, anyway?

For a little more context - the party had seen the demon speaking to a "shimmering woman" who vanished. The demon (under the Zone of Truth, which it failed to save against, despite advantage with saves - it was a Vrock) - said that it was "Bound to work with hags. But before it reveals more it wanted to know if the party plans to destroy it or release it."

The demon in question, is not willingly serving said hags of a coven. It's been bound by some form of magic the hags have that bound it to their service.

So ideally, it doesn't want to be banished back to Hell. It would rather be freed and see the party go after the hags to kill the hags, since whatever the hags have done, prevents the Vrock from taking action against them.

[Unoriginal]

It could be used in a situation where refusing to answer the question asked is seen as a defacto admission of guilt with all the consequences that go with it.

That happened in Critical Role's second season. The PCs ratted out a pirate captain who planned to overthrow the area's pirate king via cult-assisted evil demigod shenanigans, and the Cobalt Soul Monk hit the captain with the subclass's Extract Truth feature for the interrogation. Needless to say the pirate king was not fooled by the captain not responding to any of the questions.


For a little more context - the party had seen the demon speaking to a "shimmering woman" who vanished. The demon (under the Zone of Truth, which it failed to save against, despite advantage with saves - it was a Vrock) - said that it was "Bound to work with hags. But before it reveals more it wanted to know if the party plans to destroy it or release it."

The demon in question, is not willingly serving said hags of a coven. It's been bound by some form of magic the hags have that bound it to their service.

So ideally, it doesn't want to be banished back to Hell. It would rather be freed and see the party go after the hags to kill the hags, since whatever the hags have done, prevents the Vrock from taking action against them.

Demons are from the Abyss, not the Hells.

Regarding the Demon asking if the party wants to destroy them, wouldn't it be more pertinent to ask if they're willing to negotiate for the PCs to not destroy them?

Still, this situation sounds like a great and fun encounter. And Vrocks are fun to roleplay.

[JackPhoenix]

If you're in a zone of truth, what prevents you from mentally asking yourself a different question, and then answering that question aloud? Or even just saying something that just isn't the answer to an asked question.

"I didn't say the sky was red. I just said the word 'red' a short while after you warbled something about the colour of the sky, which I chose to ignore."

The GM and a heavy, throwable object close at hand.


Basically, the only think ZoT is good for is for a willing person to prove their innocence. Let the cleric cast it, they willingly fail the save and then speak a full, detailed and specific sentence that they did not do whatever they were accused of.

In fact, if I ran a judicial system and had Zone of Truth at my disposal, that would make it very easy to work around the whole issue. Just make the rule "you're guilty until proven innocent by stating in full detail that you are innocent in a zone of truth, for which you willingly fail the save". Easy peasy. (Except if the caster is corrupt and lies about the accused having willingly failed their save, which is sorta why civilized societies have 'innocent until proven guilty' as the bedrock of their judicial system).

There's no such thing as willingly failing a save.

[Valmark]

There's no such thing as willingly failing a save.

I was going to say this. Spells that allow for a willful fail explicitely say so (As an example, Calm Emotions) so it would not work for ZoT.

Yes, it's a pretty bad spell in situations where you want to extort information from a captive of any kind- I feel like it has place only where you need to know if what one said is the truth (like Unoriginal's example). Not when you need one to tell the truth.

Though regarding the OP the demon can easily wait until the paladin says something like "Me and the party want to [insert choice] you, [insert person you are answering]". Can't lie there with any kind of exploit. None that I can think of.

[ProsecutorGodot]

There's no such thing as willingly failing a save.

I'm sat here now imagining my Paladin who features a massive +19 to Charisma saves trying to explain that he's telling the truth and that he really is trying to allow the spell to affect him.

Goodness, I can't even affect myself with my own Zone of Truth.

[Keravath]

It's just in regards to Keravath's comment in post #3, suggesting that the truth effect is something you can time out in a single round which to me doesn't sound right.
That reading is the first time I've heard that interpretation.

Looking into the question of how many rolls, I was able to find

Which was more to my understanding and previous observed rulings on how other tables I've seen have ran it.

Saving against every 6 second, I can see that reading; though is sounds a bit cheesy to do the whole 'keep making this throw' song and dance. I won't say that part is wrong, just that it reeks too much of that tactic some DMs do where they keep telling you to reroll till you fail (or conversely a plot important roll that they keep saying 'roll again' till you succeed).
Roll once, that result sticks until there is a change in the situation.

Interesting. I never read it that way and haven't played it that way with any of the DMs locally.

"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."

This wording states that a creature that enters the area of effect for the first time on a turn or starts its turn there must make a saving throw. It either succeeds or fails that saving throw.

However, on its next turn, it ALSO starts its turn there. The wording here would require it to make ANOTHER saving throw. If it succeeds or fails then it follows the effect until it needs to make another saving throw. If the creature steps out of the area of the spell and steps back in, since it entered the area of the "first time on a turn" it makes another save. If they meant that save not be repeated each time the creature entered the AoE it could say "when the creature enters the area of effect for the first time. Adding "on a turn" to this implies that the creature has to roll every time it enters since there is no way it can enter that isn't "on a turn". There are many effects in 5e that allow for a saving throw every round.

As a further example, the spell sickening radiance uses the EXACT same wording:

"When a creature moves into the spell’s area for the first time on a turn or starts its turn there, that creature must succeed on a Constitution saving throw or take 4d10 radiant damage, and it suffers one level of exhaustion and emits a dim, greenish light in a 5-foot radius."

Does this mean that for sickening radiance they only get one save and then suffer the effect of the failed save on each subsequent turn? I don't play it that way personally - I use the same interpretation for both spells, but Zone of Truth and Sickening radiance use the exact same wording in terms of making a saving throw. Why would you interpret it one way for one spell and a different way for the other?

The sage advice compendium doesn't contain any official clarifications and JCs tweets are otherwise just another DM making a ruling, albeit a very experienced one ... so in the end it is another example of a case where the DM can decide how they want it to work in their game.

[Zhorn]

@Keravath, I think we have a case of miscommunication here, and for that I apologise.

Having an additional saving throw every round you are in the ZoT, or when you enter it for the first time on that round? Yes, I can see that reading. I am not saying THAT part is wrong.

Also when I said "Roll once, that result sticks until there is a change in the situation" that was to do with my talk about DMs that fish for results they want with saying to roll again when you get a result they didn't want. I will amend my previous post to make that more clear.

The ONLY part I was taking issue with was the interpreting that passing a subsequent saving throw was undoing the previous fail while the target is still within the ZoT.
If we were to use other spell language to demonstrate such mechanical behaviours, I'd point to any of the spells that specify 'you can repeat this saving throw at the start/end of your turn or when you take damage, ending the effects on a success'
Or going back to your Sickening Radiance example, passing a save does not undo the damage previously dealt or remove the levels of exhaustion caused by previous fails against the spell's saves.

Enter a Zone of Truth or start a turn inside one, make a save. I'm in Agreement
If you beat the save, but are still in the Zone on a subsequent round you will make an additional saving throw. I'm also in agreement there
The longer you are in the ZoT (multiple rounds), the more likely you are of eventually failing a saving throw and falling under the spell's effects. Makes sense, not disputing this.

Fail a saving throw on one round, then waiting till you pass on a subsequent round and lying as if no longer under the effect of the previous fail. That's my disagreement.
My opinion is once you fail against the spell's save, you shouldn't need to roll again on subsequent turns (you CAN, but it's pointless) as successes won't undo the failure.

[JackPhoenix]

Snip

They don't use the EXACT same wording, because you've missed the relevant sentence in ZoT's description: "On a failed save, a creature can't speak a deliberate lie while in the radius."

It doesn't say "The creature can't speak a deliberate lie until it succeeds on the save again."

[Sigreid]

They don't use the EXACT same wording, because you've missed the relevant sentence in ZoT's description: "On a failed save, a creature can't speak a deliberate lie while in the radius."

It doesn't say "The creature can't speak a deliberate lie until it succeeds on the save again."

IMO this is correct. The language doesn't state or imply that the effect of the spell ends on a save. To me that says that the effect is meant to be harder to resist (you have a higher chance of blowing the roll) the longer you stay in the field.

[Reynaert]

in a world where zone of Truth is a reality so are numerous magical effects and spells that can literally alter somebody's memory and perception of Truth. there's also a handful of class abilities that allow you to flat out bypass ZoT. It's basically the d&d version of the polygraph test.

I once read a sci-fi short story where there was a 100% foolproof lie-detector test which was being used to convict loads of criminals. But there wa sthis shady guy who promised to make criminals pass the test (and he could), so the story revolved around finding him. But when they did, it turned out he was actually a good guy because the way he made a criminal pass the test was by fully convincing them that they were, in fact, Good People(tm). So the treatment to be able to pass the lie-detector test was actually to rehabilitate the person into not doing crimes anymore.

[SpanielBear]

Zone of Truth coupled with Detect Thoughts (two casters obviously) would at least bypass a couple of shenanigans, or have a good chance of doing so.

[Keravath]

IMO this is correct. The language doesn't state or imply that the effect of the spell ends on a save. To me that says that the effect is meant to be harder to resist (you have a higher chance of blowing the roll) the longer you stay in the field.

OK. I can see that interpretation. :)

My interpretation comes from the assumption that a successful save prevents the effects of the spell which is not explicitly stated in the spell description.

"SAVING THROWS
Many spells specify that a target can make a saving throw to avoid some or all of a spell's effects. The spell specifies the ability that the target uses for the save and what happens on a success or failure."

In the general rule, a saving throw is made to avoid some or all of the spell's effects. The spell description as written clearly requires a new save every round even after a failed save. The spell indicates what happens on a failed save but does not indicate what happens on a successful save after having failed. However, the general rule on saving throws indicates that saving throws are made to "avoid some or all of the spell's effects". This indicates that a successful save in general prevents the spell effects from taking place. The spell does not include any text that over rides the general rule on saving throws, it only specifies what happens on a failed save.

RAW, I think the save should prevent spell effects every round depending on the saving throw made. However, I agree with you that the spell is more useful and effective with the interpretation that once a save is failed it continues to be failed but in general, anything that grants a save every turn is intended to allow the save to avoid the effects of the spell.