Can you use Invisibility, grab some gold, and have it then be invisible? Or does it only work on items on your person when the spell is cast?
Unfortunately, the rule about this is a little ambiguous.
Anything the target is wearing or carrying is invisible as long as it is on the target’s person.
This has 2 interpretations that are, as far as I can tell, equally valid.
Anything the target is wearing or carrying at the time you cast the spell is invisible as long as it is on the target’s person.
Anything the target is wearing or carrying at any point throughout the spell's duration is invisible as long as it is on the target’s person.
Luckily, someone has asked Jeremy Crawford, lead rules designer for D&D 5e, and he gave his unofficial ruling:
Only items worn/carried when invisibility is cast are invisible, but I'd let you conceal something under them.
As written, items carried or worn are invisible.
The effect of invisibility for the duration of the spell is:
A creature you touch becomes invisible until the spell ends. Anything the target is wearing or carrying is invisible as long as it is on the target's person.
The conditions of the spell specify, an object is invisible if it is carried or worn.
- Is the thing being carried by the target of invisibility?
- Is the thing being worn by the target of invisibility?
The final phrase "on the target's person" serves to clarify that the things worn or carried do not remain invisible after they are no longer carried or worn by the target. Drop a coin, and that coin becomes visible. On the flip side, pick up a coin while invisible, and the coin becomes invisible as it satisfies the first criteria of the spell effect.
Jeremy Crawford tweeted advice
The tweet from Jeremy Crawford is advice against the above interpretation. The tweeted interpretation is not supported by a simple reading of the effect, and essentially adds the absent clause "when the spell is cast". An example of a spell effect where that clause is present and the expected wording would be faerie fire
Any creature in the area when the spell is cast is also outlined in light...
Creatures entering the area during the duration are not outlined in light as that specifically only happens when the spell is cast. Invisibility has no such restriction.
Not "really", but it depends.
According to designer Jeremy Crawford you cannot make stuff you pick up invisible, but you can hide it under your invisible clothes (or bags I guess, or inside your fist maybe?). The item is still visible if you put it back down (or hold out).
And remember that dropping your own items makes them visible too because "anything the target is wearing or carrying is invisible as long as it is on the target’s person."
I would also like to add that this is one of those cases where the rule is only a little bit muddy, but both interpretations are "balanced" and logical (not silly) and can potentially create interesting situations or solve/create different problems. I mean seeing an object flying on its "own" can lead to various stories and so can things disappearing. And you can even use both. Maybe one mage's version of invisibility works slightly different to another. You can even make it a (very) minor plot point. As long as you keep it somewhat balanced (in your player's eyes at least, they can get cranky at times).
Invisibility is bestowed at the time of casting.
It cannot later be acquired.
Consider the expression used in the Monster Manual for creatures that have Invisibility as an Action rather than a spell1:
Any equipment the [creature] wears or carries is invisible with it.
For Monster Manual creatures, it is clear that equipment they pick up becomes invisible, while what they set down is visible again. If this were the intent of the spell, it could also be expressed that simply, but it is not. Both the invisibility and greater invisibility spells include the wording:
[A/a] creature you touch becomes invisible until the spell ends. Anything the target is wearing or carrying is invisible as long as it is on the target's person.
Why use "as long as it is on the target's person" rather than the simpler "with it"? In particular, why use both 'wearing or carrying' and 'on the target's person'? Isn't that redundant? How could they be wearing or carrying something if it was not on their person? How could it be on their person if they were not wearing or carrying it?
But this is not actually a redundancy, and it is more complicated than the Monster Manual language because the expressions don't mean the same thing. The longer expression used in the spell description is needed to convey a more complicated concept.
At first reading it might appear that the 'as long as' is describing the duration of the invisibility; that items set down will become visible and objects picked up will become invisible.
However, this is not the correct reading, because a duration should not be written that way. If that were the intended meaning, it would need to add the word 'for', such that it would have to say:
Anything the target is wearing or carrying is invisible for as long as it is on the target's person.
Consider the distinction between 'We'll move the game inside as long as it is raining', and 'We'll move the game inside for as long as it is raining'. The first phrase is the conditional - if it rains, then we will move the game inside, but not otherwise. The second is a duration - when it does rain, we will move the game inside for the duration of the rain, but we will go back outside when it stops.
Without the 'for', the spell description is not describing a duration, but rather a conditional clause. However, knowing that it is a conditional clause makes the meaning of the phrase puzzling. In isolation, 'Anything the target is wearing or carrying is invisible if it is on the target's person (which it much be, because as stated, they are wearing or carrying it)' is redundant.
So what is the purpose of the more complicated 'on their person' clause? The phrase actually links to the verb of the previous sentence of the spell description, "a creature you touch becomes invisible". The spell description is telling us that when you turn a creature invisible, everything on its person at that point in time becomes invisible as well. However, items it later picks up do not become invisible. "As long as it is on the target's person" means 'As long as it is on the target's person at the time of casting'. We are to understand that even if the target later picks something up and is then "wearing or carrying" it, the object doesn't become invisible. The object invisibility is one-way; it can be lost but not gained. What would be an otherwise overly complicated and redundant phrase, if it only informed us about setting objects down, is actually necessary to tell us what happens when an object is picked up, and the spell covers both possibilities.
Filling in all the implicit words, but changing the description as little as possible, it could be written as:
A creature you touch becomes invisible until the spell ends. Anything the target is [later] wearing or carrying is [also] invisible as long as it is on the target's person [when the spell is cast].
Thus, the RAI of the spell written more explicitly are:
A creature you touch becomes invisible until the spell ends. Anything the target is wearing or carrying at the time the spell is cast is also invisible, but only as long as it remains on the target's person.
1These creatures include the Duegar, Faerie Dragon, Pixie, Sprite, Quasit, and Imp