This item is absolutely broken, with a level 5 being able to throw down an illusory red dragon or, out of battle, actually throw down the entire deck, you can actually scare away the DM's boss fight with absolutely no damage taken.

Buy it, folks.

Since moving the card dispels the illusion you can't really do that. What you can do is preventing people from ambushing you, while camping. Also the more intelligent creatures will have object permanence, so they should realize, that the sudden appearance of a red dragon is somewhat weird. A high level spellcaster maybe suspects it to be an illusionary dragon (from the spell) and be somewhat scared. Maybe if you could get the illusions to come in from an obstructed point, it would work.

But it certainly wouldn't stop boss encounters consistently.

I'd just use it to scam people. Paired with prestidigitation, thaumaturgy, or druidcraft, you could put on a good show.

This is really fun to drop in the lap of a party that knows just enough about dnd to scared of a "deck of many things". You can make people fight over it, run from it, try to sell it, or steal it. All based on how you introduce a simple pouch with a deck of cards in it. 

Do the illusions emit sound?

Quote from Panzerov >>

Do the illusions emit sound?

An illusory creature appears real, of the appropriate size, and behaves as if it were a real creature except that it can do no harm.

Sounds like it can to me

I had the most fun introducing this to a low-level party that had a vague idea of what a Deck of Many Things was, drew a card from it, had an Adult Red Dragon dramatically appear before them in a cavern and spread flames all over the ceiling, and then asked them to ALL roll initiative. With dramatic boss music playing as well. XD

So, in one of my groups People just made a bunch of these and now everyone's playing Duel Monsters.

New DM here, "you can use an altered deck of playing cards to simulate the deck", does this mean you can add cards from a normal deck back into the illusionary deck and it will work?

I think it means you can take a subset of a regular playing card deck to create a prop you can use at the gaming table.

Ahhh, thanks

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I'm going to make my party "fight" a Deck of Illusions in a room that makes Illusions act as summons, and summons act as Illusions (They won't be forewarned). 

If this party of indeterminate level beats the deck, they win a Deck Of Many Things with 5 less cards than the DoIs they beat. 

I can't wait to see them sweat when they stand still to "beat" the illusion, only to get sucker-punched into a wall by a quite real Cloud Giant. 

Quote from MeatGrinderDM >>

I'm going to make my party "fight" a Deck of Illusions in a room that makes Illusions act as summons, and summons act as Illusions (They won't be forewarned). 

If this party of indeterminate level beats the deck, they win a Deck Of Many Things with 5 less cards than the DoIs they beat. 

I can't wait to see them sweat when they stand still to "beat" the illusion, only to get sucker-punched into a wall by a quite real Cloud Giant. 

 lol, how did the fight go?

Think it just means you can use a real life deck of cards to simulate the pulls in a session

depends on your DM. It doesn't specify whether or not it does but, if you have a generous DM then Yes.

well, in the context of the question I am the DM, so I guess they do make sound then :) This is going to be fun!

Could someone draw a card at random, decide they don't like that one, and put it back and draw again?

Can you pull a card and choose not to throw it so in the end you kind of get to choose the illusion but it takes a significantly longer time?

Of course you would get to choose if you were the one that made the deck and already knew what each card meant.