One of the more fun spells to player-watch. Both times it occured so far, my players forget about the job and immediately start firing questions at eachother lol

Bought the TAZ podcast shirt shirt based on this spell, because I seem to exude the effects of it at all times. It is my real life superpower. Not remotely as cool as it sounds.

Tip for anyone who gets affected by this spell:Say the truth, but in a different language. This works especially well if you're a rogue. Just say you murdered the king but in Thieves' Cant instead of common

Does Zone of Truth count as a Charm?

It doesn’t impose the Charmed condition if that’s what you’re asking. 

In my opinion, Theives' Cant might be pushing it. Though yes, it can be said in a tricky way, it does take 4 times longer to say a straight answer, so saying "I murdered the king" and taking 2 minutes to do so (assuming it takes 30 seconds to say the actual line) brings about two issues.

1. If you ever tried beating around the bush with someone who asked you something simple, it tends to be the best way to piss them off and render them violent.

2. All they'd need is to cast "Comprehend Language" or have a rogue nearby to overcome this tactic. 

That said, I'd employ devil and demon tactics with your idea. Think of the spell Summon Demon. Regardless of how successful you are, unless you know their true name, they will try and twist your commands as much as possible to follow it to the letter and use it against you. Likewise, as long as you can claim something is truthful, then you can speak it in the zone of truth:

"I was not the cause of the king's demise." (my dagger was, and I was simply the reason)

"I can justly say that I was not there when the king died." (Cause you made sure they would die after you left the room) 

"The king led his life at the cost of many people, whom I'm sure would relish the fact of his death, yet I had no qualms with the man."

Wording is key

Oh ok yeah that makes sense, wording is important too if you want to avoid telling the truth in that. I was just thinking that simply saying what you did in another language would work too. But I guess it would also be kind of suspicious if you suddenly started talking in another language as a Zone of Truth was casted on you

There are a few ways that changing your language won't work:

-Many races and fields do allow the player to learn other kinds of languages, including Primordial, which would allow understanding a lot of other languages as well. 
-Monks learn Tongue of the Sun and Moon, an ancient method of speaking that allows them to be heard and to understand all languages
-The spells Tongues and Comprehend Languages both allows a character to know what your PC is saying at all times (unless talking in Theive's Cant, but again, taking 4 words to say "yes" makes you look suspicious). With Comprehend Languages being a first-level ritual, that means anyone can learn it. 

So it would be best to learn how to word things in a misleading way than hope that those around don't have these tricks up their sleeves.

Quote from Tor888 >>

In my opinion, Theives' Cant might be pushing it. Though yes, it can be said in a tricky way, it does take 4 times longer to say a straight answer, so saying "I murdered the king" and taking 2 minutes to do so (assuming it takes 30 seconds to say the actual line) brings about two issues.

1. If you ever tried beating around the bush with someone who asked you something simple, it tends to be the best way to piss them off and render them violent.

2. All they'd need is to cast "Comprehend Language" or have a rogue nearby to overcome this tactic. 

 

That said, I'd employ devil and demon tactics with your idea. Think of the spell Summon Demon. Regardless of how successful you are, unless you know their true name, they will try and twist your commands as much as possible to follow it to the letter and use it against you. Likewise, as long as you can claim something is truthful, then you can speak it in the zone of truth:

"I was not the cause of the king's demise." (my dagger was, and I was simply the reason)

"I can justly say that I was not there when the king died." (Cause you made sure they would die after you left the room) 

"The king led his life at the cost of many people, whom I'm sure would relish the fact of his death, yet I had no qualms with the man."

Wording is key

 if the caster is smart, they won't be the one performing the interrogation, rather they'll be 30-60ft away when they take out their focus and murmur a quiet chant or prayer. When the spell takes effect the subject being questioned probably will not even realize they're under a spell (at least not immedeately) and answer truthfully until the jig is up or the spell wears off.

Quote from NatyaRudh >>

 if the caster is smart, they won't be the one performing the interrogation, rather they'll be 30-60ft away when they take out their focus and murmur a quiet chant or prayer. When the spell takes effect the subject being questioned probably will not even realize they're under a spell (at least not immedeately) and answer truthfully until the jig is up or the spell wears off.

 

Uh... No, target knows that he is under effect of the spell right away. Whats more important he is not obliged to say anything at all - if he wants he can choose to be silent. And the only one who know if target made his roll or not in each round is caster and target, so there are situations where target could use this to his advantage. 

Quote from NatyaRudh >>

Quote from Tor888 >>

In my opinion, Theives' Cant might be pushing it. Though yes, it can be said in a tricky way, it does take 4 times longer to say a straight answer, so saying "I murdered the king" and taking 2 minutes to do so (assuming it takes 30 seconds to say the actual line) brings about two issues.

1. If you ever tried beating around the bush with someone who asked you something simple, it tends to be the best way to piss them off and render them violent.

2. All they'd need is to cast "Comprehend Language" or have a rogue nearby to overcome this tactic. 

 

That said, I'd employ devil and demon tactics with your idea. Think of the spell Summon Demon. Regardless of how successful you are, unless you know their true name, they will try and twist your commands as much as possible to follow it to the letter and use it against you. Likewise, as long as you can claim something is truthful, then you can speak it in the zone of truth:

"I was not the cause of the king's demise." (my dagger was, and I was simply the reason)

"I can justly say that I was not there when the king died." (Cause you made sure they would die after you left the room) 

"The king led his life at the cost of many people, whom I'm sure would relish the fact of his death, yet I had no qualms with the man."

Wording is key

 if the caster is smart, they won't be the one performing the interrogation, rather they'll be 30-60ft away when they take out their focus and murmur a quiet chant or prayer. When the spell takes effect the subject being questioned probably will not even realize they're under a spell (at least not immedeately) and answer truthfully until the jig is up or the spell wears off.

 Per the wording of the spell, the target is aware of the spell as soon as it takes effect.

Which sourcebook did this come from?

Oops nevermind

Quote from Nublordo>>

Per the spell description, "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."

Creatures being questioned do not make a saving throw every turn. They make one saving throw against the Zone of Truth.

The spell lasts for ten minutes. If saving throws were made each turn, that would be 60 rolls per creature. Plus asking a question can take longer than six seconds, so saving throws would potentially be checked mid-question, or mid-answer. Or you would end up in silly situations where a question is asked, the creature saves, the caster realizes this, so they just ask the question again...and again...and again until the saving throw is failed.

Two aspects of the wording indicate a single saving throw is made. 1) "...a creature that enters the spell's area for the first time on a turn" means that if a creature exits the area of the spell's effect and then reenters it a second time, they don't make a second saving throw. Their original saving throw is still applicable. 2) "You know whether each creature succeeds or fails on its saving throw." "Throw" would be pluralized if multiple rolls were intended to be made during the spell's duration.

You can also think of it in terms of the wider principles of the game. Many actions, including spell casting, have a real chance of failure (e.g. dice rolls). A spell attack roll can miss resulting in a "wasted" spell slot. A creature has the opportunity to save against a Zone of Truth that they are subject to rendering it ineffective. They don't have to save 60 times, or against every individual question they are asked for ten minutes. They save once. If the save is made, there is a "failure" cost to the spellcaster - another spell slot has to be used to recast the spell, just like missing your target with a spell attack roll. If the spell is recast, the contest is reset (i.e. a significant investment has been made by the spellcaster by using a spell slot) and the creature must once again successfully save against the new spell.

Also available in the spell pool for Mark of Sentinel Human.

If the target did not see or hear the casting then the target does not know unless it's something flashy like Fireball. It is up to the DM if the spell is perceivable effect like runescript hanging in air.

You can find the information in the player handbook on p.204

It should be obvious once the spell stop the target from speaking a falsehood. The spell does not force the person to speak just stops a person from telling falsehoods when they spell fail the savings.

One thing I could not find the answer to is if somebody can purposely fail the saving roll to prove that they're speaking the truth. 

Quote from I_am_L >>

If the target did not see or hear the casting then the target does not know unless it's something flashy like Fireball. It is up to the DM if the spell is perceivable effect like runescript hanging in air.

 Except it says "An affected creature is aware of the spell", which means the spell forcibly informs the target against their and the caster's will as part of the effect.

Personally I’ve found this spell can combo pretty well with Command for quick and dirty interrogations of my poor DM’s hapless NPCs. It’s a bit of an in-joke among our group now that the first thing DM thinks of when he’s coming up with an NPC is how to avoid them spilling the beans when we stick them in a ZoT and Command them to answer.

You could just not say anything.

I actually tried this in my cure campaign they just cast tongues. After that I just started telling my life story in stead of answering the questions.