The BBEG in my campaign has been going around teaching free classes on how to make these to anyone capable of it and providing the materials for a few dozen and has been doing so for years, so this is now the single most common magic item in the campaign world and one of the first quests the group got was to figure out what the hell is going on because the King's diviners can no longer tell what the hell is going on in their own kingdom.

 Let's say the wearer is in possession of a trinket of some sort and the locate object spell is used to find the trinket.  Does locate object fail?

I would say no it doesn't. It stops the target from being located not the object

Quote from Durandals_Fate >>

Quote from Sylnin >>

Does this item prevent a target from being targeted by any Divination magics, even Detect Magic or Gift of Alacrity?

That is the straightforward reading of the spell.  A character wearing this item cannot be the target of any spell in the Divination school, even if it's a beneficial spell like Guidance, Foresight, or Telepathic Bond.

It's less obvious that "you are hidden from divination magic" is intended to have mechanical consequences for people who are not declared "targets" of a spell but may be revealed by a spell.  If someone else casts True Seeing on himself, can he see an invisible character who is wearing this item?  According to the logic of this Jeremy Crawford tweet about the identically-worded Nondetection spell, this amulet protects the wearer from being perceived by Divination magic like See Invisibility even if the wearer is not a declared target.

That suggests to me that a character under the effects of Foresight, Guidance, or Fortune's Favor would gain no benefits in combat, contests, or ability checks against a character wearing this item.  Narrating how those spells failed would be fun.

 cool, so this item has benefits and drawbacks, neat

Could it prevent location by a diety, semi-god, demon lord, arch devil or either of the dragon lords?

Quote from Geronimo5555 >>

Could it prevent location by a diety, semi-god, demon lord, arch devil or either of the dragon lords?

 i'd say yes, if i counts as divination magic

I'm guessing this does not interfere with a morkoth's lair's Regional Effect, to detect and locate any arrival on its island?

• The morkoth is aware of any new arrival, whether an object or a creature, on its island or in its sanctum. As an action, the morkoth can locate any one creature or object on the island. Visitors to the island feel as though they are being watched, even when they aren’t.

Although the morkoth is a wizard spellcaster (has scry too), this ability itself is not a divination spell, but I could see players making the argument that it is still divination magic. My interpretation is that this regional effect is an innate ability of a morkoth in its lair, not a magical effect, and it would go through the protections of this Amulet. 

Thoughts?

If you are worried about this or nondetection in combination with invisibility I wouldn't worry because using specifically divination spells magic to detect invisibility is relatively rare.  This would not stop a lantern of revealing, alarm, faithful hound, faerie fire; creatures with innate blind sight, true sight or tremor sense; or any mundane means of tracking like foot prints, sound or smell.  It's a very fallible combination.

Rock on

In a world where detect thoughts is a level one spell, these amulets would be like smartphones. Virtually everyone who could afford one would have it.

If someone used the see invisibility and True Seeing spell's do the Amulet protect you from it?

Does this amulet protect the wearer only, or the wearer AND their possessions? For instance, if I'm carrying a magical item in a non-magical satchel, is that item protected by the amulet as well?

How does this work with brand of castigation

item description says you are "hidden" from divination magic and cannot be targeted. I would allow any divination spell where the wearer themself is not being targeted, like see invisibility whose target is the caster. Something like guidance wouldn't work as the target of the spell would be the wearer.

Quote from MattyDude >>

I want to say that True Seeing would still work, but it's debating technicalities. His quote (for those who don't want to follow the link) says:

"The nondetection spell hides you from divination magic. True seeing is a divination spell."

This would imply that Nondetection whilst invisible indicates True Seeing would not find you. If that's the case, then I think this item and the equivalent spell (to a lesser degree) are somewhat overpowered.

If you can go invisible and are impossible to spot by any means, then that's a huge advantage to the user. You could still be detected by any creature that has natural Truesight, however. Personally, I'm of the opinion that for True Seeing, you're not spotting the invisible creature using Divination, but by a sense (Truesight) that just happens to be granted by Divination magic.

Since creatures who have natural Truesight can still see you, I'm fine granting this ability to Divination-based Truesight just to keep the mechanics of the sense consistent. It's also a somehat niche circumstance where you'd need both nondetection and invisibilty active, whilst evading an enemy using True Seeing.

The other part is the description specifically says (a) the target can't be targeted by any divination magic; or (b) perceived through magical scrying sensors. It doesn't technically cover being perceived using effects from spells like True Seeing, only Scrying sensors. Although the complication there is that opens up all sorts of problems, like See Invisibility. This spell technically falls within the rules since the invisible person isn't the "target" of the spell, nor is it the target of a Scry.

So for me, I'm inclined to take the definition literally. Any spell where the target is under the effect of nondetection or wearing this amulet will fail. Everything else is fair game. If using that definition this essentially means:

- any Divination spell that isn't a target of Self will fail if used against a target under this effect; and
- If you attempt to use a Divination spell with a target of Self while you yourself are under this effect, it will fail.

So technically, you or any of your party wearing this amulet will cause your beneficial Divination spells to fail. The exception here is Scrying, which is a target of Self but the 2nd effect description covers that.

No. See, your entire argument not only goes directly against Jeremy's tweet and the obviously intended interpretation thereof, as you yourself state, but it does so only because you made up a thing.

You wrongly assume that the spell True Seeing gives you a sense, instead of the spell effectively mimicing the sense magically, which is what it actually does. If it gave you a sense, it'd be a permanent physical change of some kind. It would have to quite literally alter your physiology, which it does not do. Instead, the spell is actively finding things, and reporting them to your natural sense.

This is obvious both from the description of the spell "True Seeing" and by the fact that Crawford specifically stated that you are hidden from Divination Spells, and that True Seeing is a Divination Spell. Your logic would make the item useless as if True Seeing "gave" you Truesight, then why doesn't "Detect Thoughts" do the same and "give" you psychic mind-reading? Clearly it doesn't, and instead magically mimics psychic mind-reading, which is not the same thing. Also, why would "True Seeing" end the moment you entered a null-magic zone, even if you cast it originally outside the field? Because the spell isn't changing your physiology, it's merely detecting and reporting to your brain what it normally could not see. The spell does the detection, not any new sense. You didn't gain a thing.

Furthermore, as you yourself said:

Quote from MattyDude >>

If you can go invisible and are impossible to spot by any means, then that's a huge advantage to the user. You could still be detected by any creature that has natural Truesight, however.

Except you prove your own motivation is that you don't like the power of the item, and you also prove that your arguement is moot. "...and are impossible to spot by any means." You are not impossible to spot by any means. You're just impossible to spot by any Divination Magic means. So your entire reason for being mad about this item, falls flat on it's face from the start. This is especially when you also consider that the ability to be "impossible to spot by any Divination Magic means" already comes with a drawback! As the previous poster said:

Quote from Durandals_Fate >>

Quote from Sylnin >>

Does this item prevent a target from being targeted by any Divination magics, even Detect Magic or Gift of Alacrity?

That is the straightforward reading of the spell.  A character wearing this item cannot be the target of any spell in the Divination school, even if it's a beneficial spell like Guidance, Foresight, or Telepathic Bond.

It's less obvious that "you are hidden from divination magic" is intended to have mechanical consequences for people who are not declared "targets" of a spell but may be revealed by a spell.  If someone else casts True Seeing on himself, can he see an invisible character who is wearing this item?  According to the logic of this Jeremy Crawford tweet about the identically-worded Nondetection spell, this amulet protects the wearer from being perceived by Divination magic like See Invisibility even if the wearer is not a declared target.

That suggests to me that a character under the effects of Foresight, Guidance, or Fortune's Favor would gain no benefits in combat, contests, or ability checks against a character wearing this item.  Narrating how those spells failed would be fun.

Clearly, you need to let the item work as intended, and simply have important enough and wealthy enough people like Rulers... hire guards who have natural True-sight or, more likely, Blind-sight, since that would still work and is far more "commonly available" than finding a creature one could actually hire who has natural True-sight.

Lastly, you need to verify how the so-called "natural" True-sight works. Most commonly, supposedly "natural" True-sight works the same way as magical true-sight, just without spell-slots. As in the eye "naturally" has a connection to the weave and uses that. In which case it could be argued that they are still using Divination Magic to see the creature, just not a "spell". Much like how very large dragons fly magically, because their wings alone cannot support them, and so a Null-Magic Zone should ground them, making them easier to kill. That said, usually dragons are still allowed to fly in null-magic zones... which doesn't make sense unless the magic in their flight has nothing to do with the weave and everything to do with well... them. In 5e, this actually makes sense since, according to Fizbans, dragons were flying before Mystra even made the weave, so this is resolved easily by saying "Dragons magical abilities don't use the weave, instead using the natural background magic of the world. It is other, later creatures who use the weave." (Basically, dragon use the "wild" magic of reality - and it works for them because dragons, like Tiamat and Bahamut before them, can bring Order to the Chaos of reality.) Earlier editions... not so much. But then, D&D is so freaking big that 100% perfect cohesion and zero plot-holes is nigh impossible.

Finally the item description itself erodes your claim of "this is how senses work" with the last line.

Quote from Amulet of Proof Against Detection and Location >>

While wearing this amulet, you are hidden from divination magic. You can't be targeted by such magic or perceived through magical scrying sensors.

A magical scrying sensor simply "has" a sense. It's not using a "spell" actively. Like an eye that "naturally" interacts with the weave to see invisible things using "natural" True-sight, the magical scrying sensor is embedded with magic aka "enchanted". That's all a "natural" magical organ is, a magically enchanted organ. Just enchanted "naturally" instead of unnaturally. That's it. There is zero mechanical difference, just like there is zero difference between wood that was cut "naturally" by a man using a saw, or "magically" by a mage using a spell. The wood itself is no different, only the method the wood got in that condition is different. The end result is the same. In this case, the magic is in the item or organ. One got there by way of casting a spell, the other got there by way of evolution. It's just man mimicing nature, which is done all the time. So, unless the ability to see invisible items is not magical in any way whatsoever, which would vary by creature... it could at least be argued that the item should block the so-called "natural" true-sight, as if it still relies on the weave, then it still relies on Divination Magic and is, quite literally, a "magical scrying sensor". Just an innate one. Anything that has Truesight without the weave, this argument would be moot... but with the weave? Then you have a leg to stand on when you argue this point.

That said... as I pointed out with Dragons above, RAI likely means that any creature with "natural" Truesight should probably still work. RAW though? It probably shouldn't. Regardless, your point about the spell Truesight still working is utter nonsense of the highest order, outside of Homebrew purely intended to nerf somethng for the sole reason of, "I don't like it, and I'm too lazy to think of simple workarounds like Blind-sight and Tremor-sense for the King's guards."

Tl;Dr - If you're talking Homebrew, you can obviously do what you want, but if you're arguing RAW or RAI, your argument fails either way.

What is the cost

It's in my randomly generated store

I would say that the amulet doesn't stop you from being the target of beneficial divination magic. Wouldn't the amulet's creators have this in mind? Or would they be like, "I'll make an amulet that will keep me from benefiting from this incredibly useful spell?" It seems obvious that nobody would work that into a magic item. 

One of my players absolutely loves to use Detect Magic on either random NPC’s or NPC’s accompanying the party. They’ve so far caught 2 of my BBEG’s/BBEG’s spies sent this way throughout different campaigns, leading them to get quite arrogant about BBEG’s not being able to infiltrate their party. For the most recent campaign, I had the BBEG, a seemingly innocent “middle aged” elf women who’s relatively well off and carried an assortment of magic items gained through her time as a merchant, whom also just happens to secretly run a continent-wide assassination/theives guild that’s been taking out influential figures and hoarding their wealth, wear one of these to disguise the fact she’s actually a sorcerer(she’s using the acquired funds from the guild to fuel her magic experiments and make even more magic items to distribute).

While exploring with the party for over a real life year, in game 5 years as we’re relatively slow burn with our campaigns, she slowly built up and gained the trust of the party while relaying orders via Illusory Script, writing in what seemed to be random scribbles as she “tried to get better at art.” While a few of the players got suspicious at this, after investigating and finding relatively little at first, they gave up and moved on.

Recently, they got a specific item they were looking for meant to help bring down the Assassins/Thieves guild; which is the moment our lovely middle aged elf lady struck, making a surprise attack against the party’s magic caster and landing a hit with a poisoned dagger containing crawler mucus, paralyzing the player. She then took that player hostage, nabbed the item, and teleported out of there via a Magic Circle and a magic item. The session ended there as my players just stared at me wondering what just happened and like I was the most evil person on the planet. What’s great is, they still haven’t figured out she’s a magic caster, so they’ve still got surprises ahead of them.

Nice chain

Quote from Xanathar_Ironslag >>

Dude this is a god item let me explain. if there was a trap that was triggered (with magic) if you went into the room with this you would be immune to it.

 I would not think so. First, it would have to be a divination trap. If it was triggered due to divination, yes, but if it was triggered with another school of magic, no.