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Should/could a creature tell the difference between an enemy gone invisible and an enemy that switched to the ethereal plane? For example when someone uses blink, would an enemy NPC continue attacking the spot where he was, assuming he is invisible?

I'm not sure if there is a RAW answer for this, so I would also appreciate answers based on experience.

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  • \$\begingroup\$ rocks fall (or a Fireball goes off). 1. everybody dies. 2. everybody is on another plane and is unaffected. That's obviously the major difference. \$\endgroup\$ Oct 7, 2019 at 7:56
  • \$\begingroup\$ @PeterCordes I don't doubt that there is a difference, I'm just wondering if you would notice it in the heat of battle. \$\endgroup\$
    – findusl
    Oct 7, 2019 at 8:40

2 Answers 2

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1. Invisible is not hidden

While being invisible does make you able to attempt to hide anywhere, it does not make you automatically undetected. You still make sound for example. (See the sidebar on hiding on page 177 of the PHB.) Thus it is usually clear whether a character disappeared to another plane or not. Circumstances might affect this, so the DM might rule otherwise.

2. Recognize the spell

You can attempt to identify the spell as it is being cast. You use your reaction and make an Int(Arcana) check. You can find the rules on page 85 of XGtE.

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    \$\begingroup\$ Another possible way to tell spells apart is by the components. Some spells will have VSM and other will only have a subset of those \$\endgroup\$ Oct 6, 2019 at 22:03
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    \$\begingroup\$ @Medix2 I always believed this was already included in the arcana check. Would make interesting new question, I guess. \$\endgroup\$
    – Mołot
    Oct 6, 2019 at 23:56
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    \$\begingroup\$ I always thought that was part of the arcane check too, a layman won't know the components of plane shift Vs invisibility. \$\endgroup\$
    – SeriousBri
    Oct 7, 2019 at 6:45
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    \$\begingroup\$ @findusl They are already paying attention to that person, as either that person wants to kill them, they want to kill him, or both. 5e practically assumes you are hyper-aware during combat (and mechanics are written with that in mind). But, as I said, if the circumstances warrant it, the DM can overrule this (due to large distances, noisy environment, etc.). \$\endgroup\$
    – Szega
    Oct 7, 2019 at 8:08
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    \$\begingroup\$ @Mołot I just find it near-indisputable that you can tell if somebody is moving their hand around, or moving their lips, or pulling items out of a pouch that asking it seems... out of place. So I'm asking for you to clarify that; that you believe those things are not intuitively noticed, and thus me asking the question is valid \$\endgroup\$ Oct 7, 2019 at 15:26
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The best answer to questions like this is often "discuss it with your DM". There are various opinions and perspectives that will always interfere with any supposed "universal answer".

  • Preview: My stance is "No, a creature should not simply know which effect occurred" and "Yes, they can know which effect occurred if they take the correct steps to do so." Read the following essay for why and how to do so.

Now, to give a good answer, I would would say one must consider both extremes of possible scenarios. The question appears to be asking if a character should or even could recognize the difference between seeing something go invisible or shift ethereal without additional effort on the viewer's part. (ie: they see the event, do they "just know" what happened or not?) Lets pose two theoretical scenarios on opposite ends of the possibility spectrum.

NOTE: I am going to replace casting Invisibility with casting Greater Invisibility for the purpose of this test. It makes no difference in the extreme scenario, but adds a tell in the basic on which I mention here and later.

So, for one of the most extreme scenarios... Let's assume the following:

  1. It is not a creature that any of the party can identify or make a good educated guess about its nature, it is completely alien to them.
  2. It does not breathe, does not make any passive/incidental sounds, and has no odor. It simply cannot be located by sound/smell.
  3. It always is magically hovering 1 ft. above the ground and passes through the air without disturbing it (making its movement untraceable by sound).
  4. It bears two Diamond Spell Gems (thus requires no vocal, somatic, or material components of any kind with which to identify the spell cast), one of which contains Greater Invisibility and the contains Blink.
  5. There is a massive field of Silence that envelops all entities involved. Absolutely no sound can be heard by any means by any creature.
  6. No observing entities currently have Blindsight, Truesight, Tremorsense, enhanced smell sense, Detect Magic, or other enhanced/magical senses beyond that of an average commoner human. (Because that could void the test.)

This mystery creature ends its turn immediately after activating one of the two Spell Gems. It suddenly disappears with no visual, auditory, or olfactory evidence available.

And for the basic scenario, let's assume this:

  1. It is a Human that the party knows well. Greg, from Accounting.
  2. As a Human, they breathe (but can hold their breath for some amount of time, PHB pg. 183) and may make incidental sounds.
  3. As a Human, they stand on the ground and may leave footprints and/or make noise in their movement.
  4. They do not have Subtle Spell metamagic (or any equivalent) and need to use the full components of a spell. They know both Greater Invisiblity and Blink and are able to cast either spell at their current level.
  5. They have a Component Pouch instead of a Spellcasting Focus. (This does not matter with this pair of spells, but would matter if casting basic/lesser Invisiblity.)
  6. No observing entities currently have Blindsight, Truesight, Tremorsense, enhanced smell sense, Detect Magic, or other enhanced/magical senses beyond that of an average commoner human. (Because that could still void the test.)

Greg casts one of the two spells and then immediately attempts to start holding his breath (suffocating, PHB 183) while ending his turn, desiring to be as silent as possible regardless of if he is Ethereal or Invisible, likewise suddenly disappearing immediately but with the potential to be heard/smelled by anyone close enough to do so. (Whether or not self-suffocation counts as part of the Hide action or can be done freely, like opening one's hand or stopping concentration, is up to the DM and is not the question being discussed here. It really doesn't matter either way.)

And now findusl's two questions come into play: Should the creatures viewing either disappearance (immediately) know whether the creature is invisible or out of their plane? and Can the creatures viewing either event know whether the creature is invisible or out of their plane?

Let's start easy: Should a viewer of this event know what/which happened? Answer: DM's call, because only the DM of that particular game can know if they should. BUT, as a DM and believing my fellow DM would not be terrible, I'd say "No, they should not just instantly know exactly what effect they saw. That would be anti-fun and boring, please don't be that kind of DM." Of course, there is a caveat: "Unless a character has some pre-established reason that they would instantly recognize the difference", which also leads into the other question.

So, can a viewer know which effect happened? Answer: YES! (Of course!) What really matters is just how long it will take to identify which effect happened.

In the extreme situation, it is nearly impossible because there is no difference for the observers (there is no sound or smell to detect and the source of the magic was identical). Is it Invisible? Did it leave the plane? It may be impossible to tell without additional magical means, such as Detect Magic or See Invisible. There is no good reason that the observers can simply know which is true.

However, in the basic situation there may many possible ways to tell that Greg became invisible. Perhaps Greg fails to hold his breath and now everyone can hear him or maybe he stumbles slightly and cries out or just breathes really hard in nervousness. However... that only proves that he's still there, just invisible. But, what if Greg cast Blink instead? What proof do the observers have that he is not invisible and perfectly silent? Why don't they attack his old location with the assumption that he is just invisible? Does it really make sense to assume that they can 100% know that he is actually gone and not merely invisible, on the basis that they can't see or hear him? What if he was secretly a Rogue and could Hide his sounds as a Bonus Action and the DM doesn't just spell out every little thing the NPCs do?

It's normal to claim something as true due to evidence (Greg invisible + sound/smell). It's foolish to claim something as true due to lack of evidence (Mystery Monster invisible/blink or Greg blink + no sound/smell).

In the extreme situation, a DM may require foreknowledge of a spell to even be capable of recognizing the differences of what happened, because it is virtually identical. (Don't metagame. Character's in-universe can't tell that a character's "turn ended" and triggered something via game mechanics. This is a role-playing game, remember?)

However, in the basic situation the very casting of the spell might give it away because the specific Verbal and Somatic components "should be" different between spells (especially if just shouting "Invisiblity!" vs "Blink!" for the verbal component). If one assumes basic Invisibility instead of Greater Invisibility, it also requires a material component which adds a further tell.

There is even an official method to help solve this question that is found on Xanathar's Guide to Everything page 85. This adds the Action and Reaction of "Identify a spell". (Personally, I dislike the ability to gain advantage by the caster being the same class as the character because that is free information just by telling them they have advantage. But that's how it is written.) After all, this is D&D so of course there might be ways to recognize the slight differences of a spell.

  • To avoid a certain theoretical counterpoint, Tasha's Cauldron of Everything page 116 introduces the official ability to personalize spells (or, their audio/visual effects). This shows that two people casting the exact same spell may still have unique flair. However, this doesn't go so far as to allow making one spell look like another spell. Thus it is still possible to recognize the core elements/effects of a spell.

Of course, it still comes back to the DM. If you haven't ever encountered the spell(s) involved, or they have reason to say you don't have enough knowledge about the spell(s), or maybe the effect is just too obscure to distinguish, the DM could just declare that you can't tell what the spell/effect was. Or they may have a DC that is impossible if you insist on rolling (While I don't think that's a good answer, it can be a way to deal with self-empowering players).

  • Note about considering Invisible vs Hidden, which may be an issue to resolve: All that hiding gives an Invisible creature is that they are actively masking their sounds (and maybe smells?) from detection. (See Hide, PHB pg 192 and Hiding, PHB pg 177) Per the RAW for Unseen Attackers and Targets (PHB pg 194), being Invisible always grants all the benefits of being an Unseen Attacker/Target for as long as you remain invisible. So it is often inferred that any creature is always making at least some incidental noise which can be heard from whatever distance to pinpoint its location... (The idea that any incidental sound instantly and constantly gives away both the exact distance and direction to within a 5 ft. space is obviously quite nonsense without a specialized racial trait or feat. Even worse that you can just gain advantage in whatever way to then make it a normal attack against a target that you cannot see and have mere sounds to guide your dagger/sword/bow/lightning. But, sadly the rules seem to leave that as a valid interpretation which people abuse to no end and they can/will argue it until you get sick of wasting your time with them or give in/up.)

  • Note on "hearing a creature's location": There are no rules to help here, at all. At best, there are two charts found on two DM Screens (neither chart exists in any rule book, official or otherwise, to my knowledge). One has an "Audible Distance" chart and the other has an "Audible Distance" sub-chart as part of an Encounter Distance chart. The distances listed are exactly the same for both:

  • "Trying to be quiet: 2d6 × 5 feet" (10-60 ft.)

  • "Normal noise level: 2d6 × 10 feet" (20-120 ft.)

  • "Very loud: 2d6 × 50 feet" (100-600 ft.)

Interestingly, if that chart was used for a game, it would inherently allow a creature to "try to be quiet" without taking any Action (such as Hide) and thus reduce the distance from which they can be heard and anything beyond that range couldn't hear them at all to locate them. Likewise, it would give a mechanic to use for spellcasters trying to be sneaky with their spellcasting.

Why this chart is not in the DMG is beyond me. It is so small yet would add a potential mechanical distinction between Hidden (resists being heard at any distance), quiet (inaudible outside a small/moderate range), normal volume (inaudible outside a larger range), and loud (audible within a large range, though not beyond that). And be a big help for all questions involving invisibility.

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  • \$\begingroup\$ Is that chart on an official DM screen? \$\endgroup\$
    – SeriousBri
    May 15 at 17:30
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    \$\begingroup\$ I'll let you decide what counts as "official". (Does it being sold by Wizards or having their logo make it official even if it is just an accessory?) The listing on D&D site: dnd.wizards.com/products/dungeon-kit The chart cannot be found in any sourcebook, so if your definition of official would be what applies to Adventurer's League, to my understanding it would not be. Regardless, it would be a useful guide/starting point for use, as I have used it here. \$\endgroup\$ May 16 at 22:29

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