Does an illusion have scent outside its area of effect?

[greenstone]

There was a comment in the long "is a created bonfire a bonfire?" thread that made me stop and go "huh?". The comment was that arguing that the scent of an illusion doesn't leave its area of effect was wrong.

I've always played it exactly this way. If a caster creates a major image (20ft cube) of a fruit tree, then you can only smell the blossoms if you are inside the 20ft cube.

Now, thinking about it more, I wonder if I've been playing it wrong for decades.

After all, you can see the illusionary tree from outside the area; you can hear it from outside the area, so why can't you smell it?

What are your thoughts?

[ender241]

Yes.

(Please for the love of Ilmater don't let this be another 10 page debate)

[Psyren]

Yes it does, and you provided the correct logic as to why - if you needed to be inside the illusion's area of effect to perceive it, then not only could you not smell an illusion without being on top of it, you couldn't see or hear it without being on top of it either. We can probably all agree that's not the intent.

As for how far away you can be from an illusion and still smell or hear it, that's a DM call. Major Image for example requires you to use "sounds, smells, and temperature appropriate to the thing depicted," and prevents you from causing damage. So a major image of a campfire will shed light, can feel warm (maybe even hot?) and crackle convincingly, but standing on it won't burn you.

[Thunderous Mojo]

This might depend upon the wording of the spell in question.
In practice, there are not many illusion spells that affect the olfactory sense.

Phantasmal Force would supply an olfactory component…but only to the targeted creature.

The wording of Mirage Arcana would also seem to limit the spell’s effects to a one square mile zone. So no traveling odors, but Mirage Arcana, as is, has a huge area of effect.

I also don’t think Hallucinatory Terrain’s verbiage would have the scents spread past the 150’ cube illusion the spell creates.

What other Illusion spells create olfactory effects?

The wording of Programmed Illusion does not preclude that the illusion also produces odor.

[Mastikator]

Illusions can be smell't only by those who dealt it.

[Schwann145]

Illusions can be smell't only by those who dealt it.

Aaaand... /thread

[Segev]

Yes it does, and you provided the correct logic as to why - if you needed to be inside the illusion's area of effect to perceive it, then not only could you not smell an illusion without being on top of it, you couldn't see or hear it without being on top of it either. We can probably all agree that's not the intent.

As for how far away you can be from an illusion and still smell or hear it, that's a DM call. Major Image for example requires you to use "sounds, smells, and temperature appropriate to the thing depicted," and prevents you from causing damage. So a major image of a campfire will shed light, can feel warm (maybe even hot?) and crackle convincingly, but standing on it won't burn you.

Excellently put.

The confines of the illusion's space are the space from which the sensory impressions can originate. You can have your minor illusion of the sound of a lion roaring come from the entire five foot cube, or anywhere within it, but not from two different five foot cubes. However, as far away as the DM deems appropriate, people can hear the lion roar. It's just that the "speaker" from which the sound is emitted must lie within and be no bigger than the five foot cube.

The same is true of the twenty-foot cube for major image. You can place your scent-source anywhere within that cube, and make it as big as you like as long as it fits within that cube, but it is still localized within that cube. So you could have this huge bowl of fruit loops, but Toucan Sam could still follow his nose to the 20-foot cube (and even to where, within said cube, you placed the scent source) from outside of it.

[Tanarii]

No. At least not if you're a human-like PC. The ability to smell isn't good enough we'd be able to smell an illusion from any distance, outside of some very exceptional circumstances.

[Psyren]

Excellently put.

The confines of the illusion's space are the space from which the sensory impressions can originate. You can have your minor illusion of the sound of a lion roaring come from the entire five foot cube, or anywhere within it, but not from two different five foot cubes. However, as far away as the DM deems appropriate, people can hear the lion roar. It's just that the "speaker" from which the sound is emitted must lie within and be no bigger than the five foot cube.

The same is true of the twenty-foot cube for major image. You can place your scent-source anywhere within that cube, and make it as big as you like as long as it fits within that cube, but it is still localized within that cube. So you could have this huge bowl of fruit loops, but Toucan Sam could still follow his nose to the 20-foot cube (and even to where, within said cube, you placed the scent source) from outside of it.

Agreed.

I'll also add that the size limitations and "appropriateness" clause can be used to establish limits of some kind too. Major Image can make a 20-foot cube of fire for instance - so that governs how far away someone can feel the heat from it. Producing heat equivalent to a forest fire or an erupting volcano would be out.

[Segev]

No. At least not if you're a human-like PC. The ability to smell isn't good enough we'd be able to smell an illusion from any distance, outside of some very exceptional circumstances.

I think this is actually tacitly self-negating. If "as long as you're a human-like PC" is the requirement, that means it acknowledges that something with a better sense of smell would potentially smell it from further away.

And I disagree, anyway. I have some wildflowers that grow in one section of my yard. I can definitely smell them even if I'm not standing on top of them.

When visiting a farm, I assure you I can smell the animals even when not in the same 20-foot cube they're in.

[Psyren]

Yeah, a 20-foot cowplop would very likely be detectable from decently far off.

But as you get closer and the smell doesn't cause any kind of harm to you, that would give you reason to suspect you're dealing with an illusion.

[Segev]

Yeah, a 20-foot cowplop would very likely be detectable from decently far off.

But as you get closer and the smell doesn't cause any kind of harm to you, that would give you reason to suspect you're dealing with an illusion.

Pretty sure bad smells don't usually do damage. :P

[Tanarii]

When visiting a farm, I assure you I can smell the animals even when not in the same 20-foot cube they're in.
Having recently been on a dairy farm ... okay fair enough. Position reversed, depending on what it's an illusion of the smell of. :smallamused:

[JLandan]

Pretty sure bad smells don't usually do damage. :P

A bad enough one might cause a condition. How big a cowplop requires a Con save? Or more practical: Can an odor, illusory or otherwise be bad enough to force a Con check on a caster?

Prestidigitation specifies harmless, but will do an odor. Also not much range.

[Mellack]

Having recently been on a dairy farm ... okay fair enough. Position reversed, depending on what it's an illusion of the smell of. :smallamused:

To give you a more pleasant though, I have certainly smelled my neighbor's bar-b-que from more than 20 feet away.

[Psyren]

Pretty sure bad smells don't usually do damage. :P

Agreed, not HP damage - but how bad does a smell need to be before it can interfere with a creature's ability to breathe or impose a condition - I do wonder.

Irrelevant for the illusion, which can't have these effects, but for the real thing it could be.


To give you a more pleasant though, I have certainly smelled my neighbor's bar-b-que from more than 20 feet away.

Indeed - and their grill probably fits in a 20ft. cube also.

[Segev]

Agreed, not HP damage - but how bad does a smell need to be before it can interfere with a creature's ability to breathe or impose a condition - I do wonder.

Irrelevant for the illusion, which can't have these effects, but for the real thing it could be.



Indeed - and their grill probably fits in a 20ft. cube also.

Yeah, for the real thing, a bad enough smell would have to be something the DM homebrews, or that the module spelled out. (Troglodytes might give some guidance.)

[GooeyChewie]

Can an odor, illusory or otherwise be bad enough to force a Con check on a caster?

Yes... and no. Page 204 of the PHB says "The DM might also decide that certain environmental phenomena, such as a wave crashing over you while you're on a storm-tossed ship, require you to succeed on a DC 10 Constitution saving throw to maintain concentration on a spell." So it could cause a check for concentration, if you clear it through your DM. Probably best to bring up the idea before the game, rather than trying to pull it mid-session.

[JLandan]

Maybe, if you could get a stinking cloud up as a reaction.

For example: Ready action to cast stinking cloud if a caster starts casting.

If successful, it would prevent a caster from casting next round.

[Psyren]

Yes... and no. Page 204 of the PHB says "The DM might also decide that certain environmental phenomena, such as a wave crashing over you while you're on a storm-tossed ship, require you to succeed on a DC 10 Constitution saving throw to maintain concentration on a spell." So it could cause a check for concentration, if you clear it through your DM. Probably best to bring up the idea before the game, rather than trying to pull it mid-session.

I'd say a real smell could do that but an illusion (at least, not Major Image) couldn't. (Mirage Arcane might though.)

[Dr.Samurai]

Re: Can a smell be bad enough to cause a condition

I don't recall if this is military tech or law enforcement anti-riot stuff, but apparently there is a malodorant device that disperses an odor so bad it tricks the brain into thinking it's inhaling something toxic and it causes a flight response.

That would be more in line with an enchantment though as far as spells go. I don't think an illusion would do that.

[greenstone]

Illusions can be smell't only by those who dealt it.

One of my players last night said the same thing. :smalltongue:

[Psyren]

Re: Can a smell be bad enough to cause a condition

I don't recall if this is military tech or law enforcement anti-riot stuff, but apparently there is a malodorant device that disperses an odor so bad it tricks the brain into thinking it's inhaling something toxic and it causes a flight response.

That would be more in line with an enchantment though as far as spells go. I don't think an illusion would do that.

I'd say what I was getting at was that there are probably non-spell phenomena that could produce smells of this caliber - think a midden of corpses in a warm cellar, the heart of a bog, the smoke from burning chemicals, or a mushroom-filled cave choked with spores etc - that the DM could reasonably rule causes damage to you or other deleterious effects if inhaled.

I'm further saying you could produce an illusion of such things (provided whatever you create fits in the spell's area and otherwise conforms to its rules.) And such an illusion would, to an unknowing perceiver, be detectable as far away as the real thing of that size. But getting closer to the source would not have the deleterious effects mentioned above, which in itself would likely prompt your Investigation check to realize that {illusion of thing} doesn't stink nearly as bad as {thing} probably should given your proximity.

[Keravath]

A bad enough one might cause a condition. How big a cowplop requires a Con save? Or more practical: Can an odor, illusory or otherwise be bad enough to force a Con check on a caster?

Prestidigitation specifies harmless, but will do an odor. Also not much range.

No. Major Image states the following: "You can't create sufficient heat or cold to cause damage, a sound loud enough to deal thunder damage or deafen a creature, or a smell that might sicken a creature (like a troglodyte's stench)."

I think it is pretty clear that the intent is that spell can create heat/sound/smell to go with the visual illusion but they can't be strong enough to have any mechanical effects. So although a real troglodyte smells bad enough to make someone feel sick, an illusory one just smells bad with no mechanical effect.

[Segev]

No. Major Image states the following: "You can't create sufficient heat or cold to cause damage, a sound loud enough to deal thunder damage or deafen a creature, or a smell that might sicken a creature (like a troglodyte's stench)."

I think it is pretty clear that the intent is that spell can create heat/sound/smell to go with the visual illusion but they can't be strong enough to have any mechanical effects. So although a real troglodyte smells bad enough to make someone feel sick, an illusory one just smells bad with no mechanical effect.

Yep.

Thinking about it, as a DM, I might still ask players to make a Constitution saving throw, and tell them nothing bad happens regardless of their roll. That would be sufficient to obscure it from somebody who isn't yet suspicious, but to give a clue as well based on nobody failing the saving throw if they decide to then make the Investigation check.

[JLandan]

Yep.

Thinking about it, as a DM, I might still ask players to make a Constitution saving throw, and tell them nothing bad happens regardless of their roll. That would be sufficient to obscure it from somebody who isn't yet suspicious, but to give a clue as well based on nobody failing the saving throw if they decide to then make the Investigation check.

The D in your DM is Devious.

[Psyren]

Yep.

Thinking about it, as a DM, I might still ask players to make a Constitution saving throw, and tell them nothing bad happens regardless of their roll. That would be sufficient to obscure it from somebody who isn't yet suspicious, but to give a clue as well based on nobody failing the saving throw if they decide to then make the Investigation check.

I wouldn't. What if one of them rolls a 1? Do they get a different result than everyone else?

[GooeyChewie]

I wouldn't. What if one of them rolls a 1? Do they get a different result than everyone else?

Why would they? The whole point is that somebody might “fail” and have nothing happen, tipping them off that the smell is an illusion.

[Segev]

I wouldn't. What if one of them rolls a 1? Do they get a different result than everyone else?


Why would they? The whole point is that somebody might “fail” and have nothing happen, tipping them off that the smell is an illusion.

What GooeyChewie said. Also, in 5e, 1s don't auto-fail, and there ARE some ridiculously-low save DCs in the monster manual.

Sprite arrows, for instance.

[Psyren]

Why would they? The whole point is that somebody might “fail” and have nothing happen, tipping them off that the smell is an illusion.

But if everyone rolls high then they won't get that hint due to thinking they just succeeded normally. It's counterintuitive.

[GooeyChewie]

But if everyone rolls high then they won't get that hint due to thinking they just succeeded normally. It's counterintuitive.
I suppose it is counterintuitive in that players normally want to roll high. At the same time, I think it makes sense in the case of trying to avoid something that you don’t know can’t hurt you. For instance, suppose the party comes across what seems to be an enchanted sword whirling around in a doorway. The PCs would likely think they need a Dex save or Acrobatics check to pass unharmed; the one who “fails” and has the sword go through them will be the one to realize what seemed like an enchanted sword was a harmless illusion.

[Segev]

But if everyone rolls high then they won't get that hint due to thinking they just succeeded normally. It's counterintuitive.Not really. It just means the illusion was convincing. They're used to being able to take such stenches without flinching, so won't notice that it's not as strong as normal.


I suppose it is counterintuitive in that players normally want to roll high. At the same time, I think it makes sense in the case of trying to avoid something that you don’t know can’t hurt you. For instance, suppose the party comes across what seems to be an enchanted sword whirling around in a doorway. The PCs would likely think they need a Dex save or Acrobatics check to pass unharmed; the one who “fails” and has the sword go through them will be the one to realize what seemed like an enchanted sword was a harmless illusion.

Yep. It's just a matter of where you draw the line on what constitutes verisimilitude.

Now, where I might feel badly about it is if the ystart spending resources on passing that save. A portent to ensure the low-Con guy doesn't gag would be a waste, and I'm not sure I'd let him do that. I might give it back to him later or something.

[Psyren]

I suppose it is counterintuitive in that players normally want to roll high.

That, and also, rolling high is supposed to be better than rolling low in this game. But if you roll high and remain oblivious (compared to someone who rolled low and got additional information with their "success"), that feels incredibly janky.

[Chronos]

Sometimes being good at one thing means being bad at another. For instance, I'm highly tolerant of spicy mustard. In game terms, I suppose you could say I have a high bonus to my save vs. mustard, if you liked. One time, I was at a Chinese restaurant with my family, and commented that the mustard was completely non-hot, and I wondered if they had substituted just ordinary French's or something. My mom took a tiny taste, and immediately reached for the water, because it was much too hot for her.

In other words, because I was so good at resisting mustard, I was bad at telling the difference between real mustard and fake mustard.

[Segev]

That, and also, rolling high is supposed to be better than rolling low in this game. But if you roll high and remain oblivious (compared to someone who rolled low and got additional information with their "success"), that feels incredibly janky.

I understand your point, but I disagree that this is a problem. If the players already suspect it's an illusion, they don't need the hint. If they don't suspect it's an illusion, the fact that the stench isn't overwhelming them probably isn't a huge problem.

As for better examples of when rolling high isn't necessarily a good thing, if you roll high enough to see through the deception of a bog hag who grossly out-levels the party but was just trying to slip away without trouble, she may decide to kill you rather than let you go when you know she was there.

Sometimes, rolling high fails to give you an advantage. That doesn't mean you failed.

Honestly, I'd be hard-pressed to see a situation where failing to even attempt to learn the troglodyte was an illusion was so costly that you'd lament having rolled well on Constitution saves that could've given you the hint otherwise.

[Psyren]

As for better examples of when rolling high isn't necessarily a good thing, if you roll high enough to see through the deception of a bog hag who grossly out-levels the party but was just trying to slip away without trouble, she may decide to kill you rather than let you go when you know she was there.

This is a weird example. Rolling high doesn't mean she knows you saw through her deception - your actions upon learning the truth do that. Don't react and you're fine.

If I were at a table where I got punished for a high roll I wouldn't be happy playing there much longer. Agree to disagree it is.

[GooeyChewie]

If I were at a table where I got punished for a high roll I wouldn't be happy playing there much longer. Agree to disagree it is.

It isn’t a matter of being punished for rolling high. It’s just that you tend to get more information from getting a success when you expect failure (or vice versa) than from a clear success (or failure). Suppose, for example, the party is facing an enemy of unknown AC and would like to figure that number out. You make an attack and roll a 27. Sure, you hit, but you didn’t learn anything about the target’s AC. The next player hits with an 11, and now you know a lot more about the target’s AC. You were not punished for rolling high, but they did get more information than you did.

[Psyren]

"Expectations" shouldn't have anything to do with a smashing success yielding less benefit than a marginal one. All winning with a natural 1 tells me is that the roll was pointless to begin with.

[Segev]

"Expectations" shouldn't have anything to do with a smashing success yielding less benefit than a marginal one. All winning with a natural 1 tells me is that the roll was pointless to begin with.

Not to be snarky, here, but doesn't that mean that you feel you didn't get more information from rolling low than you would have rolling high, and therefore the problem you're expressing concern over (i.e. that rolling low is BETTER than rolling high in this situation) doesn't arise? :smallconfused:

[Psyren]

Not to be snarky, here, but doesn't that mean that you feel you didn't get more information from rolling low than you would have rolling high, and therefore the problem you're expressing concern over (i.e. that rolling low is BETTER than rolling high in this situation) doesn't arise? :smallconfused:

What I'm saying is that, if rolling low would tell me "this is actually an illusion", I would expect to get that same information from rolling high as well, even if the DM has to openly tell me.

And I would know that because, if I rolled a 1 and was told "actually you're fine" my next question would automatically be "wait, is this hazard even real?"

[Segev]

What I'm saying is that, if rolling low would tell me "this is actually an illusion", I would expect to get that same information from rolling high as well, even if the DM has to openly tell me.

And I would know that because, if I rolled a 1 and was told "actually you're fine" my next question would automatically be "wait, is this hazard even real?"

I suppose "canary in a coal mine" is actually a pretty good example here.

Let's say you're exploring a coal mine that's become infested with something that doesn't care about "bad air." You bring a canary, because the canary is going to hopefully die before you guys succumb and give you warning.

Unfortunately for you, the canary makes very high saves when the danger starts hitting, leading you to keep going deeper and exposing yourselves to more hazard.

Rolling high is always supposed to be good, right? Should the canary rolling high tell you that the air has gone bad?

[Psyren]

I suppose "canary in a coal mine" is actually a pretty good example here.

Let's say you're exploring a coal mine that's become infested with something that doesn't care about "bad air." You bring a canary, because the canary is going to hopefully die before you guys succumb and give you warning.

Unfortunately for you, the canary makes very high saves when the danger starts hitting, leading you to keep going deeper and exposing yourselves to more hazard.

Rolling high is always supposed to be good, right? Should the canary rolling high tell you that the air has gone bad?

But that illustrates my stance perfectly. The whole point behind the canary is that it's impossible for them to survive in air quality conditions bad enough to kill the humans. In other words, it's impossible for them to no-sell a save that a human would fail. If that were possible, then the canary would be an awful barometer and be swiftly replaced by something else, and whoever bought canaries for this purpose would feel cheated. Just like I would at a table.

Your analogy would be like if the illusion could kill the canary, but it could somehow survive the real thing.

[ew_of_chiswick]

I would say that in this case (an illusory smell that wouldn't cause any effect on the PCs), I don't think calling for a roll of any kind is correct; not because of the low roll / high roll confusion(*), but because it's a roll that cannot be failed (or passed, depending on how you look at it).

I'd probably say that I would just have the party do nothing, and if someone asks, "Do we feel like the smell is overpowering?" (or something like that), I'd reply with, "It's a very strong odor but you don't feel like it's affecting you at all." Basically, if a player had enough wherewithal to ask about it, they'd get a small hint towards it being an illusion.

(*) I would probably not feel cheated or wronged at all, probably the opposite. I would most likely think it was a fun subversion of expectations.

[ew_of_chiswick]

I suppose "canary in a coal mine" is actually a pretty good example here.

Let's say you're exploring a coal mine that's become infested with something that doesn't care about "bad air." You bring a canary, because the canary is going to hopefully die before you guys succumb and give you warning.

Unfortunately for you, the canary makes very high saves when the danger starts hitting, leading you to keep going deeper and exposing yourselves to more hazard.

Rolling high is always supposed to be good, right? Should the canary rolling high tell you that the air has gone bad?
I don't subscribe to "rolling high is always supposed to be good"(*), but I don't think this is a great example. In 5e mechanics, a canary would basically be a free use of what could be called detect unbreathable air. Giving it saving throws is counter to its purpose.

(*) D&D is a role-playing game, so outside of combat, what's "good" or "bad" is how your characters react to the situation. And even then, in the illusory odor case, I would say "not being incapacitated by the smell" is a good outcome. It's the OOC inference that because there was a saving throw, it must be real, that is the "bad" thing... but that was something the players have control over.

Maybe a better example is your party coming across an NPC in a town on their way to a mission. They roll insight on the statement, "We haven't seen anything suspicious in our town," and roll high enough to learn the NPC is lying. Turns out, a much more powerful enemy than they are ready to fight has taken over the town, and they all die in the process. In that case, the high roll was bad, because they used the incomplete information the high roll provided to make a suboptimal decision.

[Segev]

But that illustrates my stance perfectly. The whole point behind the canary is that it's impossible for them to survive in air quality conditions bad enough to kill the humans. In other words, it's impossible for them to no-sell a save that a human would fail. If that were possible, then the canary would be an awful barometer and be swiftly replaced by something else, and whoever bought canaries for this purpose would feel cheated. Just like I would at a table.

Your analogy would be like if the illusion could kill the canary, but it could somehow survive the real thing.I am being slightly unfair with my example, yes, because in D&D the canary wouldn't be a creature making saves but rather a tool that's part of a survival check or something.

However, I'm also not entirely sure why you care if you get a hint as to the smell's falsehood, since interacting with the illusion will cause it to be revealed, anyway. :smalltongue:

More seriously, I just don't see this as a problem. The DM can call for rolls any time he thinks the result of the roll will be important/interesting.


Maybe a better example is your party coming across an NPC in a town on their way to a mission. They roll insight on the statement, "We haven't seen anything suspicious in our town," and roll high enough to learn the NPC is lying. Turns out, a much more powerful enemy than they are ready to fight has taken over the town, and they all die in the process. In that case, the high roll was bad, because they used the incomplete information the high roll provided to make a suboptimal decision.
That works, too.

[GooeyChewie]

…would feel cheated. Just like I would at a table.

I’m not understanding in what way you would be cheated. The point of calling for a roll in this case would be that the DM wants the players to have an opportunity to realize something is weird and that they might should investigate for illusions. The alternative is not “you figure it out if you roll high;” the alternative is nobody rolls and no hint is given at all.

How about a more direct example? Suppose the party is walking along when some rocks come flying towards them out of nowhere. Everybody rolls a Dex save to dodge! The players who roll high get out of the way. The player who got a 1? They falter right into the path of a rock!… which goes right through them because it is an illusion. The character with the high rolls did do better at dodging. But part of doing better is not experiencing first hand the effects of failing, good or bad.


I'd probably say that I would just have the party do nothing, and if someone asks, "Do we feel like the smell is overpowering?" (or something like that), I'd reply with, "It's a very strong odor but you don't feel like it's affecting you at all." Basically, if a player had enough wherewithal to ask about it, they'd get a small hint towards it being an illusion.

It’s true that this situation wouldn’t normally require a roll. But if the DM just says no roll is required, it really just tells the party that the smell isn’t *that* bad. Calling for the roll, then revealing that it wasn’t really needed if somebody “fails” is the hint.

Edit: Please note that the whole idea was put for as a means of giving a hint. It’s definitely table-dependent as to how well it would go over. My table would love it; Psyren’s might hate it, and both are okay.

[Chronos]

I don't think I've ever been in a situation where I was punished for rolling high, but I have been in a situation where I was rewarded for rolling low. We were making our way through the Underdark, and came across a settlement of stone giants. Plan A was to just sneak past them, but my rogue absolutely flubbed his stealth check. So they saw us, and demanded to know our business. Once we got to talking, it came out that they were mad at the same Drow that we were, and not only didn't hinder us, but actually helped us a bit. Help that we never would have gotten, had I not failed that stealth roll.

[ender241]

Yeah, the idea that rolling low is occasionally more beneficial in the long run than rolling high makes perfect sense to me. Because a single ability check is an isolated attempt to complete a task. Rolling high means that you did better at that specific activity, not that you are guaranteed to move closer to completing your overall goals. Lots of good examples that other people have already mentioned, but I can envision lots of ways that failing at a task provides information or opportunities that succeeding would not. I could see that becoming frustrating if a DM routinely creates situations where rolling low is beneficial, but occasionally doing it can create some interesting and unexpected results that enrich the story, imo.

[SpanielBear]

I regularly run a 5e game with Lovecraftian elements.

My players frequently pray to fail perception rolls to avoid seeing the horrifying truth hidden beneath the illusion of quotidian reality.

Like other people have said, rolling low or high indicates how well one has succeeded at a specific task. If the task you are undertaking happens to be ill-considered, a failure is going to benefit you more than success.