D&D 5E Major Image (Spell): When should a creature use its action to examine something that it believes is real?

[bbrown12]

Note that if a PC has a passive investigation strong enough to find the illusion, I would always allow them to discern the illusion right off the bat...

Passive skills are a tool for DMs to quickly determine a skill check without the need of a roll. It's NOT that you do something "passively". This has been misunderstood since playtest. So, the asnwer is no. A creature does not automatically succeed in the investigation check. Certainly not, if the spell says the creature has to use its action. Somehow, this is the purpose of the spell: to waste an enemy's action.

 

[Gadget]

In the example given in the OP, it would depend on how vigilant and alert the guard patrol is, as determined by the DM. If a very professional and alert guard noticed a bush that was not there on their last circuit of the area, they may well investigate; even if they do not suspect an illusion and I would allow a role. This would be somewhat rare, unless the illusory bush was in a highly inappropriate/noticeable spot. As for in combat use, if something just shows up at of nowhere, I would allow an investigation check in most circumstances, the benefit of the spell is forcing the opponent to waste an action on an investigation check in combat. However, if the illusion is very clever, well done, and plausible (i.e. reinforcements coming in a battle to force the enemy to retreat), I would forego the investigation check and just have the NPC/Monster react accordingly (i.e. retreat).

 

[seebs]

Hey guys,

the Major Image spell has no saving throw. Let's say a creature has no reason to arouse "natural suspicion" (like a guard patrol seeing a bush that hasn't been there before). So, creatures that see the image believe it to be real.

Furthermore, a creature has only two possibilities to find out, it's an illusion:

1. It physically interacts with the illusion (and sees things going through). This one is pretty simple and clear.
2. It takes its action to examine the illusion (therefore it makes an Investigation check against the Spellcasting DC).

My question is: When would a creature use its action to investigate something that it believes is real?

No one would ever come up with the idea to investigating a real creatures/characters/etc.

So, the only situation I can imagine is the following:

• Creature A finds out the image is an illusion, because of physical interaction (it has no reason to investigate) - maybe even by chance.
• Now, it shouts to his allied Creature B "Hey, this is an illusion!".
• Creature B has still no indications to take the image as an illusion, because it seems so real (sound, smell, temperature, etc.), except Creature A telling him for some strange reason.
• So, Creature B still needs to find out himself. He can always do so by physical interaction, but now it has well-founded indications that the image might be an illusion (because Creature A told him so).

So, the only way for a creature to take its action to investiagte the image is, if it has well-founded indication from outside (e.g. other creature).

Am I right?

TL;DR: I would never offer an NPC/Player the possibility to use its action to investigate an illusionary image, if it has no well-founded indication from outside (e.g. other creatures telling him). A creature believes the image is real, so why would it come up with the idea of investigating it? In addition, it always can find out it's an illusion by physically interacting with it (maybe by chance).

I think your assumption that no one would ever investigate a real thing is wrong. Even in our world, where mirages are fairly rare and specialized, people absolutely investigate things they think they see but which seem weird to them in some way, or which aren't expected, or which look like they could be mirages.

More importantly, "believes is real" is sort of begging the question. What makes you assume that they believe it's real just because they can't tell it's an illusion? And in a world where illusions are a thing, "I check that out" is a plausible course of action.

So... No, I don't think you're right. You can investigate a thing for any reason. You can do it because you have a list of procedures and one of the steps is "investigate every such object to ascertain whether or not it is an illusion". You can do it because it's a solid object that you aren't expecting. You can do it because you think there's an illusionist. You can do it because you just plain feel like it. That's all fine! People can, and do, check things out for no particularly solid reason except a vague hunch.

 

[jgsugden]

Passive skills are a tool for DMs to quickly determine a skill check without the need of a roll. It's NOT that you do something "passively". This has been misunderstood since playtest. So, the asnwer is no. A creature does not automatically succeed in the investigation check. Certainly not, if the spell says the creature has to use its action. Somehow, this is the purpose of the spell: to waste an enemy's action.

The rules generically say that an action is required to make any ability check, yet the rules for passive checks override that general rule. Here, I also believe that the text in the illusion requiring an investigation check is overruled by the passive check rules. We all know these rules are ambiguous, but we have to make rulings and I pick the fun ruling.

It is heroic to have heroes see through illusions at a glance. It makes a good story. That is what we want in a role playing game... playing a role in a good story.

 

[jaelis]

yet the rules for passive checks override that general rule.

There are some special rules for passive perception. Otherwise AFAIK passive checks use the same rules as regular checks, except for the die roll.

Of course, that doesn't mean you shouldn't play the way you like.

 

[Hawk Diesel]

Here's my 2 copper pieces. Anyone remember the video where you're instructed to count the passes with a bunch of kids tossing each other basketballs? Then afterwards the teacher asks who noticed the guy in the gorilla costume walk in the middle of the scene and you're like "Wtf you talking about?" And then the teacher replays it and sure enough a guy in a gorilla suit walks in the middle, even stops to wave at the camera, the slowly walks out of frame.

My point here is that wasn't even an illusion and a significant number of people don't see the ape if they don't expect it.

So in D&D, I would say even with interaction there's a lot that could go unnoticed if people are focusing on something else and people are not prepared.

Guard duty is boring and tedious. It would take WAY more than an out-of-place bush to get someone's attention. I mean, think about driving to and from work. How much stuff happens that goes under your radar because you're on autopilot?

My point is that as a DM, unless the illusion is outrageous or SUPER obvious, an NPC would never even pay it mind, let alone spend energy to investigate.

 

[The Crimson Binome]

So in D&D, I would say even with interaction there's a lot that could go unnoticed if people are focusing on something else and people are not prepared.

Guard duty is boring and tedious. It would take WAY more than an out-of-place bush to get someone's attention. I mean, think about driving to and from work. How much stuff happens that goes under your radar because you're on autopilot?

My point is that as a DM, unless the illusion is outrageous or SUPER obvious, an NPC would never even pay it mind, let alone spend energy to investigate.

As long as you're fair about it, that's the important part. If the NPC isn't going to even get a chance to notice a bush that's out of place, then be sure that you treat the PCs similarly when they're in the same sort of situation. Avoid promoting it to their attention by even describing it the first time it appears.

 

[Sword of Spirit]

Hey guys,

the Major Image spell has no saving throw. Let's say a creature has no reason to arouse "natural suspicion" (like a guard patrol seeing a bush that hasn't been there before). So, creatures that see the image believe it to be real.

Furthermore, a creature has only two possibilities to find out, it's an illusion:

1. It physically interacts with the illusion (and sees things going through). This one is pretty simple and clear.
2. It takes its action to examine the illusion (therefore it makes an Investigation check against the Spellcasting DC).

My question is: When would a creature use its action to investigate something that it believes is real?

No one would ever come up with the idea to investigating a real creatures/characters/etc.

So, the only situation I can imagine is the following:

• Creature A finds out the image is an illusion, because of physical interaction (it has no reason to investigate) - maybe even by chance.
• Now, it shouts to his allied Creature B "Hey, this is an illusion!".
• Creature B has still no indications to take the image as an illusion, because it seems so real (sound, smell, temperature, etc.), except Creature A telling him for some strange reason.
• So, Creature B still needs to find out himself. He can always do so by physical interaction, but now it has well-founded indications that the image might be an illusion (because Creature A told him so).

So, the only way for a creature to take its action to investiagte the image is, if it has well-founded indication from outside (e.g. other creature).

Am I right?

TL;DR: I would never offer an NPC/Player the possibility to use its action to investigate an illusionary image, if it has no well-founded indication from outside (e.g. other creatures telling him). A creature believes the image is real, so why would it come up with the idea of investigating it? In addition, it always can find out it's an illusion by physically interacting with it (maybe by chance).

I can't remember ever having a PC examine something to see it if were an illusion. It may have happened, but it must be really rare.

Consequently, the NPCs almost never do it either.

You have the right of it -- this should almost never come up unless someone they have reason to believe/trust points out something as an illusion. Otherwise it just works. Cool huh?

 

[bbrown12]

Thanks for all your answers! I found some nice indications about how to rules this!

 

[UngeheuerLich]

I allow passive investigation to give hints that something is not quite right there.

I also let you use investigation to search for clues when they are in plain sight but not obvious as clues. (Everyone sees them but only the investigator recognizes them as clues...)
So if you investigate a certain object, you might notice that this is a fake... ähm... illusory object.
(Passive) Perception might give you hints. You may notice a stream of air that seems to come out of the wall. You may also search for hidden objects and notice something strange about the wall.