D&D 5E Minor Illusion question

[Warmaster Horus]

Can an object created by minor illusion, which can't product sensory effects, block light?

Example: A room is lit by a torch in a wall sconce. Minor Illusion is cast to create an iron box bolted to the wall around the torch. Does this plunge the room into darkness?

 

[jodyjohnson]

I'd rule it can block line of sight to the torch but not block the light in general.

You'd see a strangely lit room with an iron box on the wall. Probably grant advantage on the disbelieve given the unusual lighting.

Kind of like old video game where the light sources didn't match the surfaces correctly.

 

[KarinsDad]

I'd rule it can block line of sight to the torch but not block the light in general.

You'd see a strangely lit room with an iron box on the wall. Probably grant advantage on the disbelieve given the unusual lighting.

Kind of like old video game where the light sources didn't match the surfaces correctly.

This solution sounds interesting.


This is a hard ruling to make.

On the one hand, an illusion (by definition) blocks (or at least alters) light. It almost would have to. Otherwise, everyone could see through it to whatever is behind it already reflecting or generating light.

On the other hand, once an illusion is disbelieved, that character can see through it. In the case of an illusion designed to block light (or to hide anything really), that character can now see the light (or see through the illusion). However, light is light. Either the illusion blocks it (or alters it), or it does not. If one disbelieving character can suddenly make the light shine through, it would be strange indeed that the light was not blocked until one character made the Investigation check (or alternatively, one character interacted with the object).


I think that your solution is probably the only one that really makes sense. Light still goes through an illusion, it just kind of becomes part of the illusion and is changed in color / hue / pattern / intensity to match the illusion. Intensity is the real kicker. Does bright light suddenly become dim and when disbelieved, becomes bright again? A tough nut to crack.


I guess that I would rule that except for intensity, the color / pattern / hue of the light changes to match the illusion, but that the brightness stays the same. As per your solution, it makes the area strangely lit.

 

[hoffrg86]

Nice elaboration KD, I would also agree with it being slightly off and with Jody on the advantage on a roll.

 

[Tormyr]

The illusion has two "states": one for those who see the illusion, and a transparent version for those who have disbelieved it. Both situations are existing at the same time for different creatures. So my understanding is there is something about looking at the illusion (which is not really there) that alters the viewers mind. The viewer either interacts with it and reveals it is an illusion or investigates it and figures out it is an illusion. At this point, the illusion loses its hold on the viewers mind, but the illusion itself (the magic supporting it for a minute) does not change.

So at that point, I would think that any scientific explanations about light and what not go out the window. The magic of the illusion does not block light, it alters the viewer's perception of whether the light (and visible objects on the other side of the illusion) are blocked.

Honestly, I think this explanation makes the spell more interesting to me. The party enters a room lit by a single torch, and the party (somehow) has no active sources of light and no darkvision (yeah, work with me here). As the party enters the room something casts minor illusion on the torch to block it out. At the point the party sees the illusion around the torch, the magic takes effect in their mind and the light in the room goes out. The party is now in (as far as their minds will accept) darkness. Meanwhile, if someone in the room had cast minor illusion on the torch, they know that it is an illusion, and the room does not go dark for them. The party can either activate other light sources or investigate or interact with the illusion around the torch, at which point the lights come back on for anyone successful with that.

So my ruling would be "If the illusion was a real object, how would it affect the environment in terms of vision and light?" and go with that alteration of the viewer's mind until the viewer works out what is going on, but it does not actually​ block the light.

 

[Warmaster Horus]

What's interesting is that the other, higher-level illusion spells are all Int(Investigation) saves, too. To me this means that illusions are a challenge to your rationality and not a physical phenomenon, because, as Tormyr points out, those who save by investigation (disbelieving?) them have the effect 'muted' while those who don't still see the illusion in it's fullest, until they interact with it (hand passes through).

By this measure I would assert that an iron box surrounding a torch would APPEAR to plunge the room into darkness for those who 'see' it and believe what it is.

 

[Croesus]

The party is now in (as far as their minds will accept) darkness.

My concern with this ruling is that the illusion is confined to a small area (the box), not the entire room. The light reflecting off the walls and objects in the room is not covered by the illusion, so would still be there. Having the mind somehow calculate 1) the only light in the room is from the torch, and 2) a box now covers the torch, so the entire room has to be dark, even though it really isn't dark - that sounds more like hypnosis than illusion to me. I'm more inclined to go with KD's suggestion that the room is still lit, but anyone who sees the illusory box can't tell where the light is coming from.

 

[KarinsDad]

The illusion has two "states": one for those who see the illusion, and a transparent version for those who have disbelieved it. Both situations are existing at the same time for different creatures. So my understanding is there is something about looking at the illusion (which is not really there) that alters the viewers mind. The viewer either interacts with it and reveals it is an illusion or investigates it and figures out it is an illusion. At this point, the illusion loses its hold on the viewers mind, but the illusion itself (the magic supporting it for a minute) does not change.

So at that point, I would think that any scientific explanations about light and what not go out the window. The magic of the illusion does not block light, it alters the viewer's perception of whether the light (and visible objects on the other side of the illusion) are blocked.

Honestly, I think this explanation makes the spell more interesting to me. The party enters a room lit by a single torch, and the party (somehow) has no active sources of light and no darkvision (yeah, work with me here). As the party enters the room something casts minor illusion on the torch to block it out. At the point the party sees the illusion around the torch, the magic takes effect in their mind and the light in the room goes out. The party is now in (as far as their minds will accept) darkness. Meanwhile, if someone in the room had cast minor illusion on the torch, they know that it is an illusion, and the room does not go dark for them. The party can either activate other light sources or investigate or interact with the illusion around the torch, at which point the lights come back on for anyone successful with that.

So my ruling would be "If the illusion was a real object, how would it affect the environment in terms of vision and light?" and go with that alteration of the viewer's mind until the viewer works out what is going on, but it does not actually​ block the light.

That is one possibility, but Illusion magic that affects the mind tends to be high level illusions (and always has been in D&D).

There is also:

"Some illusions create phantom images that any creature can see, but the most insidious illusions plant an image directly in the mind of a creature."

Since any creature can see a Minor Illusion from any range, it wouldn't seem to be mind affecting. Instead, it seems to affect the environment (i.e. the light reflected or generated by anything behind/under the illusion) and only if the creature figures it out does that creature get the paradigm shift to see the imperfections in the illusion that allow that creature to see past it.

It's not that the illusion is affecting the mind of the creature, it's that the creature is focusing his attention to figure out the difference (as per real world illusions that if perceived one way, look one way and if perceived another way, look another way).


From your description here, if Minor Illusion were cast before anyone entered the room, the room from outside would appear to be lit until someone enters the room and sees the illusion. That doesn't seem to be what the cantrip is capable of doing.

 

[Tormyr]

That is one possibility, but Illusion magic that affects the mind tends to be high level illusions (and always has been in D&D).

There is also:

"Some illusions create phantom images that any creature can see, but the most insidious illusions plant an image directly in the mind of a creature."

Since any creature can see a Minor Illusion from any range, it wouldn't seem to be mind affecting. Instead, it seems to affect the environment (i.e. the light reflected or generated by anything behind/under the illusion) and only if the creature figures it out does that creature get the paradigm shift to see the imperfections in the illusion that allow that creature to see past it.

It's not that the illusion is affecting the mind of the creature, it's that the creature is focusing his attention to figure out the difference (as per real world illusions that if perceived one way, look one way and if perceived another way, look another way).


From your description here, if Minor Illusion were cast before anyone entered the room, the room from outside would appear to be lit until someone enters the room and sees the illusion. That doesn't seem to be what the cantrip is capable of doing.

Regarding the light, I can totally buy that the light still shines through, and the effect of the light source (lighted objects in the room) is readily visible to all.

However minor illusionstill seems like it needs to be mind affecting to some degree because two different creatures can investigate it, one makes the Intelligence (Investigation) check and sees through it (literally), while the other fails the check and sees a solid object. The creature who passes the check realizes that it is an illusion and can see through it, but that does not change the nature of the illusion for everyone else. The other creature keeps on staring at a solid box until they interact with it or pass a check. Even when viewed from a far distance, there is something about viewing an illusion that causes the brain to throw an exception, at least temporarily.

So from hearing the feedback, I think it could make sense to have the room lit as normal, and the shadows in the room indicate that the light source is the box. The color of the light, intensity, and everything else about the light should not change. If it is a particularly bright light, it may even be a little painful to look at the box. Or if the illusion was an awning outside on a bright day, if the sun was on the other side of the illusion, the viewer might have a chance of blinding itself if it does not look away from the underside of the awning. This ruling might also make sense because otherwise minor illusion could encroach a little on the darkness spell if the illusion can actually block light.

I appreciate these discussions. It is nice to work through this stuff ahead of time rather than to have to come up with a ruling at the table that may not be completely though through.

So how does this sound: The illusion is there, but it blocks no light. The illusion tricks the viewer's mind into thinking there is something there.

 

[Tony Vargas]

A long, long time ago, someone I was gaming with created 'an Illusion of Darkness,' basically, used Phantasmal Forces to cast what looked like Darkness 15' radius. No on disbelieved, because Darkness 15'r was a well-known spell, and he essentially created darkness he could see through (and so could any allies he quietly tipped off who made their saves).

Phantasmal Forces was a 3rd level spell back then, and Darkness 15r was 2nd. Maybe that wasn't so abusive.

Should a cantrip do the same thing?

I'd rule against this trick out of hand, as a DM. It's obviously too much. The rationalization could be that the illusion isn't really of an iron box, but of a whole room plunged into darkness, and that's far beyond the AE of the spell. That'd leave open 'illusions of darkness' using a more powerful spell. An illusion of a 'formless grey mist' could serve a similar purpose - blocking LoS, but not light, itself.

Another consideration is the interaction of light sources and invisibility. If an invisible character is carrying a light source, is the source invisible? Does it still illuminate the area? In past eds, that's been the case.

Another consideration is that being affected by an illusion generally requires seeing it, and if the room is plunged into darkness, you won't be able to see the iron box, so you won't be affected by the illusion, which means the iron box isn't there for you, which means the room is lit, which means you can see the iron box, which means you're affected by the illusion, which means the room is plunged into darkness, which means you can't see the iron box....