The typical crystal ball, a very rare item, is about 6 inches in diameter. While touching it, you can cast the scrying spell (save DC 17) with it.
The following crystal ball variants are legendary items and have additional properties.
Crystal Ball of Mind Reading. You can use an action to cast the detect thoughts spell (save DC 17) while you are scrying with the crystal ball, targeting creatures you can see within 30 feet of the spell’s sensor. You don’t need to concentrate on this detect thoughts to maintain it during its duration, but it ends if scrying ends.
Crystal Ball of Telepathy. While scrying with the crystal ball, you can communicate telepathically with creatures you can see within 30 feet of the spell’s sensor. You can also use an action to cast the suggestion spell (save DC 17) through the sensor on one of those creatures. You don’t need to concentrate on this suggestion to maintain it during its duration, but it ends if scrying ends. Once used, the suggestion power of the crystal ball can’t be used again until the next dawn.
Crystal Ball of True Seeing. While scrying with the crystal ball, you have truesight with a radius of 120 feet centered on the spell’s sensor.
Notes: Scrying, Detection
So, like, unlimited number of uses per day?
Yes
How much can you sell it for?
Well, Yes and No. The Crystal Ball works as your focus for the Scrying spell. That means: It enables you to cast the scrying spell. How often depends on how many spell slots you have.
that's not right...it says nothing about it being a focus and it also does not limit the use of scrying to spell slots much less any requirement to even have the spell, therefore a fighter could use a crystal ball
Which would be curious, as the Spell itself says you need a a focus like a crystal ball to cast it in the first place.
The 1000 gp crystal ball that is a material component for the spell is a mundane item. This is a very rare magic item that requires attunement. If the scry spell required you to be attuned to an item that was otherwise useless to you, it would be a terrible terrible spell.
And a magic item that grants you permanent limitless access to a 5th level spell would be a very broken, thus very terrible magic item^^
Also, as per the spell's description, you may as well use other items as your material component instead of a crystal ball. The crystal ball itself is just the base item for the other, more powerful versions of itself.
It's clear that it's not just listing it as a spell focus. Why would it specify that it has a spell DC of 17? If you are casting it, it should use your own DC.
I would rule that you're allowed unlimited casting. Similar to the Ring of Telekinesis (also a 5th level spell, also a very rare item) where the wording is unambiguous.
Well, I obviously can't argue against the fact that, as written, the interpretation of this can go both ways, so this is rather a debate over opinion and intention than on the "item as written"
However, I would highly advice any DM who runs any camping that is remotely based on anything the PCs might not know and/or have to find out to not hand them limitless use of magic like that. The moment you hand them this item, interpreting it like that, they will know everything that's goin on everywhere in your world, with pretty much any NPC and faction they can think of. This will end any mystery in your campaign instantly. If you want this item to be able to cast the spell itself, as to this interpretation, you have to house-rule some repercussions to prevent them form goin like "ok we sit in this town for a week and uncover the campaign plot".
its a very rare magic item that is not "up to debate" or anything like that. Any creature attuned to the item can cast the Scrying spell at will. As for your "house rule", well, you can do that without the item as well. it just might take a little while longer, if you have your campaign set up in such a way that this is possible. anyway, Magic item rules, directly from the book:
"Some magic items allow the user to cast a spell from the item. The spell is cast at the lowest possible spell level, doesn't expend any of the user's spell slots, and requires no components, unless the item's description says otherwise. The spell uses its normal casting time, range, and duration, and the user of the item must concentrate if the spell requires concentration."
You are gonna have stroke when you see the rod of resurection.
As you say, it's a 5th level spell. If it does break your whole campaign, you are not a very good DM. By the time any player character can get his hands on something like this and not loose it (hired thiefs and assassins exist, especially if they are not discrete about having it which I promise they won't be), you should be far beyond level 9 and have access to the spell anyway. Sure, it would not unlimited but you would still be able to cast enough times in a whole week to learn whatever you could learn through this method.
In other words : if this item breaks your campaign, the simple existence of the spell would have broken your campaign anyway.
Players need to choose what to scry, and can't scry a place they've never seen or a person they have never heard of, and people get WIS saves as well.
That's before getting into having NPCs who can see invisible, who know languages the players don't (if there's not a rogue/druid, thieves' cant/druidic can be good grabs), and even just clever use of euphamism in cases where NPCs just happen to be in mundane earshot of present people.
The typical crystal ball, a very rare item, is about 6 inches in diameter. While touching it, you can cast the scrying spell (save DC 17) with it.
It says you can cast it. It is a very rare item. There are no limits to using it. Just remember a creature can only be targeted by the scrying spell once per day. Other then that, cast as many times as you'd like.
I don't think that's true. Only if the target succeeds on it's save are you limited to once per day - this is to prevent you from continually attempting to scry until you succeed.
Not necessarily true. Yes, they could in theory scrye any target infinite amounts of times and this can remove mystery but there are also enchantments that prevent such invasions of privacy. There is also detect invisibility that allows them to see the sensor, and dispel magic that allows them to well ... dispel it.
Make sure your Big Bad is capable enough to do these things, or smart enough to hire someone that can. Or develop an enemy for your campaign that doesn't care if it is seen or spied on and you're golden even if your party pulls one of these balls out of a random loot table.
Remember too the casting time of Scrying: 10 minutes of casting, followed by (up to) 10 minutes of observing. This means that you can't be watching a given target for more than 50% of the time (assuming they keep failing their saving throw), and who's to say that the crucial conversations/actions will definitely occur during the 50% of time the PC is watching? So that's one limit on this powerful magic item. Other comments have covered other kinds of limits that might apply to creatures in your campaign. These include:
• magic wards against divination spells such as Nondetection, Mind Blank, Sequester. Or of course the spell specifically designed for this issue: Mordenkainen's Private Sanctum. Any high-powered NPC worth their salt (and with the necessary financial resources) will ensure that they pay to have their HQ covered by this spell. Also means that any level 7+ Wizards who keep their ears open might get offered good money to go and cast this spell everyday on an aspiring BBEG's lair (or even just a rich noble's palace/manor, etc.).
• the ability to see invisible objects (truesight/True Seeing, See Invisibility, Detect Magic, etc)
• not being on the same plane of existence (Rope Trick, Mordenkainen's Magnificent Mansion, Etherealness, Plane Shift, etc)
• darkness (natural or magical), if the target creature has darkvision (or Devil's Sight) and the creature casting Scrying does not.
• all kinds of illusion spells that might hide or give a misleading impression of what the target creature is actually doing
And finally, one creative use of Contingency for savvy mages would be to cast See Invisibility on yourself whenever you are the target of a Scrying spell!
Wouldn't you be able to start casting it the moment the spell succeeds? Meaning you'd finish the casting as soon as the duration ran out?
This item has no limits to how much you can cast scrying with the exception of if the target succeds the save they become immune to the spell for 24 hours. If you rule that this magic item uses spell slots so should any other magic item that lets you cast spells, such as the hat of disguise, the wand of magic missiles, the rod of ressurrection ect ect. This renders said items completely and utterly useless.
I also disagree that it will remove all mystery of the game. Matthew Mercer in C2 of critical role used scrying to great effect to drop breadcrumbs to his players. In a majority of campaigns I've played in, half the time players don't even realise there is a mystery to begin with, and this orb is actually my solution to allowing them to try and find clues to allow them to start piecing puzzle pieces together. My goal with a mystery is for my players to solve the bloody thing.
Finally, for mystery campaigns, this isn't game breaking. Any villain with half a brain will splash out on an Amulet of Proof Against Detection (an uncommon item), to make them immune to divination magic such as scrying.
Casting a spell with a casting time longer than 1 action takes your concentration, so the moment you started casting scrying again your original cast would end.