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The shape water cantrip has the following description:

Casting Time: 1 action
Range: 30 feet
Components: S
Duration: Instantaneous or 1 hour (see below)

You choose an area of water that you can see within range and that fits within a 5-foot cube. You manipulate it in one of the following ways:

• You instantaneously move or otherwise change the flow of the water as you direct, up to 5 feet in any direction. This movement doesn’t have enough force to cause damage.


• You cause the water to form into simple shapes and animate at your direction. This change lasts for 1 hour.


• You change the water’s color or opacity. The water must be changed in the same way throughout. This change lasts for 1 hour.


• You freeze the water, provided that there are no creatures in it. The water unfreezes in 1 hour.

If you cast this spell multiple times, you can have no more than two of its non-instantaneous effects active at a time, and you can dismiss such an effect as an action.

I have 3 scenarios I have cooked up as an AT Rogue to use this cantrip for cheating and forgery (detailed below):

1. Cheating at cards


2. Cheating at dice


3. Forgery

Cheating at cards

I have a deck of blank cards ... theoretically, I can paint the cards with water and "change the water's color". With this in place, given that the other players are holding there cards within the 5ft^3 box ... I should be able to manipulate the state of the cards simply by recasting (eg: swap an ace and a two).

• would this setup be 1x instance of "no more than two of its non-instantaneous effects active at a time" or 1x per card in the deck?

Cheating at dice

I have a set of blank ivory dice ... a cubic frame with 6x faces. Holes in place of painted dots would allow ice to show through. By coloring each hole as black or white, I could effect the count on each side while all the water maintains contact with itself.

• Assuming 2x Dice each constituting an instance of "no more than two of its non-instantaneous effects active at a time" ... would this pass even the most stringent interpretations of the Shape water spell?

Forgery

I have a blank legal document, or better yet ... one that has been filled out with information totally irrelevant to my use case (diff name, diff legal context). Can paint it with water and overwrite some or all of the document with the intention that it reverts back to its original wording once the 1h duration ends?

• Do I have to remain in the "Range: 30 feet" for the shaped water to remain?

I know I have asked multiple questions here, but the underlying theme is the same:
What are the limitations for using shape water for cheating and forgery?

One Line of This Spell Makes These Ideas Difficult

There is an essential phrase you (originally) left out of your description of the Shape Water cantrip (Elemental Evil Player's Companion, p. 21, bold added).

• You change the water’s color or opacity. The water must be changed in the same way throughout. This change lasts for 1 hour.

All of your ideas involve seem to involve selectively changing part of the water to one color, and other parts to another color (e.g. changing the water on the legal document to spell out different words in some places, changing the color to be white in some parts of the die and black on others, changing the water to be white on some parts of the card and red on others to represent an ace, etc.). But since "the water must be changed in the same way throughout," this would most likely be impossible.

It might be possible to write a specific message in water on a paper or card, and then turn all that water black and opaque (or clear) as you desired. But you couldn't alter the message to fit your needs. You could argue that you can "cause the water to form into simple shapes and animate" and thus rewrite the messages or cards as you see fit. But "simple shapes" tends to mean polygons (i.e. closed shapes like triangles and squares), and usually would rule out more intricate shapes like writing.

Finally, it's quite debatable whether a wet card would be considered "an area of water" (or whether a wet document would be anything other than suspicious). You've suggested (in a comment) that the card would not be wet, but covered in "a light layer of colored frost." Note, however, that the spell does not give you the ability to melt ice, but only to freeze water. And ice cannot be moved or altered in appearance or shape by this spell: only water.

What are the limitations for using shape water for cheating and forgery?

The limitations are:

• Maintaining line of sight and a clear path to the water.




• Having water available to manipulate and not a dry color.




• Being able to somehow hide your spellcasting from those that could discern what you are doing.




• Following a strict adherence to the allowed uses of the spell enumerated in its description.

Other considerations:

• Your uses of shape water are imaginative, though I imagine one does not roll dice or play cards with wet surfaces.




• You shape water with that spell, not evaporated colors; are your play surfaces still damp?




• Spells are not necessarily subtle, unless you are using the sorcerer's Subtle Spell metamagic. This would imply there is a good chance that someone will be on to you and your cheating.




• You would have to cast this spell presumably more than once to continue to manipulate the water to your liking.




• It is not immediately clear that shape water can manipulate ice or frost; you would have to wait for it to melt or dismiss that as an Action.