D&D 5E Minor Illusion...can it be cast over other objects?

[Jefe Bergenstein]

I for one think it's fair to say that in a world of magic and artificers, a regular shaped coin is doable. Yes, it's "medieval", but, being fantasy, is actually "medieval plus".

Don't forget that in almost all settings, there is an actual god of trade that probably has dictates on minting to prevent this sort of BS by 1st level chump wizards. They bit coins in our world, and there wasnt magic oozing from every pore. Ringing the coins or simply walking 6 feet with one (and outside the illusion radius) for purchases over a gold piece should be common enough - its the equivalent of the counterfeit pen every gas station has.

 

[MrHotter]

If the player was trying to use a pile of coppers instead of gold I would say that as soon as the merchant picks up a piece to look at it he would know it was not gold. Just by looking at the coins the merchant would be able to make an investigation check to see past the illusion.

The player is making the illusion of a pile of gold, not changing the way the copper coins look. He would have to be sure the pile of illusion coins is larger than the pile of real coins. The same trick could be used to make a pile of rocks look like coins, or make a pile of coins from nothing.

I could see how it would be useful to have minor illusion when trying to con a merchant, but I would think it would take some planning and a bit of luck. I don't think the illusion would work unless they get the merchant to not touch the coins.

 

[Springheel]

Of course the most complicated questions are things like

Can you make an illusion of a mirror that shows something you cannot personally see? What does it show? Something you made up, or the real reflection?
What about an illusion of a portal to a place you cannot see? What does it show? Again, something you made up, or the real location?
Does an illusion of a 5' cube of thick fog get dispelled if objects pass through it?

All of which have very strange effects no matter how you answer.

I would say no, you can't create illusions of things/places you can't see. A mirror wouldn't look like a mirror; it would either look like a painting behind glass (if you guess at what it would reflect) or just blank glass. Same thing with a window.

As for fog, passing through it would reveal it to have no physicality (no sense of wetness). And it wouldn't react to your moving through it like real fog would, so that would be enough to reveal it to be fake.

 

[Rhenny]

I certainly let players create small bushes or rocks to hide behind. But, if the NPC/foe knows the location well, I give him/her/it a free perception check to see if he notices something's not quite right.

 

[Gwarok]

Good point about how the coins will be shaped different and weigh different, especially gold coins, but I think that it would work quite well gemstones though.

 

[Saeviomagy]

I would say no, you can't create illusions of things/places you can't see. A mirror wouldn't look like a mirror; it would either look like a painting behind glass (if you guess at what it would reflect) or just blank glass. Same thing with a window.

So you are saying that you can't make an illusion that reflects light? That rules out basically everything that isn't totally matte, leaving every illusion looking like a poorly done painting and failing to work on more than one person at a time. Illusion becomes a joke school, usable only for all three of it's spells that don't actually make illusions.

Of course if properties that affect light are replicated, then you can create illusions of things like lenses and shaped mirrors and they work to full effectiveness, meaning you could theoretically conjure up an illusion of a telescope (an incredibly powerful one, to boot: it's only a bit smaller than the hubble) and it will work flawlessly. You can also create a 5' perfect magnifying glass and do some serious burning.

Of course the argument that you duplicate everything about the illusion that effects light means that you should also duplicate it passing through a portal... but most of the implications for that are simply too powerful for a low level illusion spell.

Long story short, adjudication is needed and it's not at all clear where the line should be drawn. My personal line would be that a mirror, magnifying glass or telescope would work for optical purposes, even the ludicrously powerful version. The portal would also work, but requires both ends of the portal to be within the space of the illusion.

As for fog, passing through it would reveal it to have no physicality (no sense of wetness). And it wouldn't react to your moving through it like real fog would, so that would be enough to reveal it to be fake.

What if you throw an object through it?
Why would it not react to movement? Are illusions perfectly static? Doesn't that rule out illusions of flags, rope, cloth and anything else that is flexible? Are the only illusions possible with minor illusion matte, 100% solid items that are stationary in space? That seems like it's much, much worse than a single aspect of the prestidigitation spell (which can create genuine small items out of thin air)!

 

[Springheel]

Illusion becomes a joke school, usable only for all three of it's spells that don't actually make illusions.

We're talking about a cantrip here. Obviously a cantrip is going to have lots of limitations.

So you are saying that you can't make an illusion that reflects light? That rules out basically everything that isn't totally matte, leaving every illusion looking like a poorly done painting

I never said anything about reflecting light. I said I wouldn't let the spell reflect (or otherwise show) an image of something you can't see. Although you raise a good question...do illusions react believably to changes in light? If I make a chair, does it cast a genuine shadow which moves if the light moves, or is the shadow part of the illusion and therefore static?

Why would it not react to movement? Are illusions perfectly static?

Again, we're only talking about the "Minor Illusion" cantrip, and the implication of the text is that it creates only static images. Even if the DM rules otherwise, the spell specifically says it has no physicality, so it wouldn't move in response to something physical passing through it.

 

[EvanNave55]

I would say he has cover. If someone misses due to his cover bonus, they hit the illusionary rock at a point that he's hiding behind it, dispelling the illusion and causing the arrow to pass through the illusion and into him.

Of course the most complicated questions are things like

Can you make an illusion of a mirror that shows something you cannot personally see? What does it show? Something you made up, or the real reflection?
What about an illusion of a portal to a place you cannot see? What does it show? Again, something you made up, or the real location?
Does an illusion of a 5' cube of thick fog get dispelled if objects pass through it?

All of which have very strange effects no matter how you answer.

- I'm not really sure about mirrors, that's highly DM dependent and I'd have to see what the situation is if it were to come up in a campaign of mine.

- You could create what looks like a portal, but you would choose what the other side looks like. Otherwise you could use it like a higher level divination spell and it's definitely not meant to be used like that.

- Fog would definitely work fine and wouldn't be dispelled.

Of course this is just all IMO.

 

[Saeviomagy]

We're talking about a cantrip here. Obviously a cantrip is going to have lots of limitations.

Cantrips do enough damage to kill a man, create real objects (prestidigitation can produce anything that fits in your hand, bonfire creates a real bonfire), make 5' cubes of water reshape themselves and then turn to 5' cubes of ice, dig 5' pits etc.

But apparently making a realistic looking mirror is beyond the pale. Oh think of the children!

I never said anything about reflecting light. I said I wouldn't let the spell reflect (or otherwise show) an image of something you can't see. Although you raise a good question...do illusions react believably to changes in light? If I make a chair, does it cast a genuine shadow which moves if the light moves, or is the shadow part of the illusion and therefore static?

... a reflection in a mirror IS reflected light. What you are saying is that you can't make a realistic looking illusion of anything shiny. Because that would be overpowered, or something.

And now apparently you're keen to say that illusions don't respond to moving light sources. At what point do you just ban illusion spells so players don't take the trap option?

Again, we're only talking about the "Minor Illusion" cantrip, and the implication of the text is that it creates only static images. Even if the DM rules otherwise, the spell specifically says it has no physicality, so it wouldn't move in response to something physical passing through it.

No, the implication is gotten through reading another illusion spell and deciding that since minor illusion does not have some text from that spell, it cannot create illusions that have any movement. I've already shown that the reading makes no sense, because that text isn't present in most illusion spells, which would render many of them non-functional.

- You could create what looks like a portal, but you would choose what the other side looks like. Otherwise you could use it like a higher level divination spell and it's definitely not meant to be used like that.

So would you say that you can create an appearance of depth without the physical space for that depth to fit in (ie - can you create a roadrunner-style fake tunnel on a wall?)

 

[Springheel]

And now apparently you're keen to say that illusions don't respond to moving light sources.

Care to point out where I've said that? Or do you read minds?

I've already shown that the reading makes no sense, because that text isn't present in most illusion spells, which would render many of them non-functional.

You ignored the second part of the sentence, where I said that doesn't matter. "the spell specifically says it has no physicality, so it wouldn't move in response to something physical passing through it."

The fog wouldn't move when you threw something through it, which would reveal it to be an illusion.