Is a character unseen by tremorsense while jumping?

Question

Tremorsense is described as:

A monster with tremorsense can detect and pinpoint the origin of vibrations within a specific radius, provided that the monster and the source of the vibrations are in contact with the same ground or substance.
Tremorsense can't be used to detect flying or incorporeal creatures. Many burrowing creatures, such as ankhegs, have this special sense.

Assuming that tremorsense allows a monster to "see" other creatures that are touching the ground as is covered by option 1 of this answer and also assuming that the monster is unable to see the character except via tremorsense, does jumping cause a creature to be unseen by the monster?

As an example Raflannan the thief is facing a fearsome Ankheg in an area covered by heavy fog. Raflannan runs and jumps firing his crossbow at the Ankheg while midair. Is Raflannan's attack rolled at disadvantage due to not seeing his target or is it a regular roll because the advantage of being unseen cancels out disadvantage?

Exempt-Medic · Accepted Answer · 2020-11-10T02:07:51.887

12

It is up to the GM

As far as I can tell, there aren't clear-cut rules on this; what we do know is that tremorsense doesn't work against flying creatures and that jumping is not flying.^{[citation needed]} Does this mean that tremorsense can detect jumping creatures? I don't know.

We also know the following from the "Unseen Attackers and Targets" section:

[...] When a creature can't see you, you have advantage on attack rolls against it. [...]

Whether tremorsense literally counts as "seeing" isn't entirely clear. I personally would say that it does as otherwise creatures with nothing but tremorsense would always grant advantage to their attackers and that hardly seems fair.

But can they "see" you while you're jumping? I have found no rule describing this, so I believe it is up to the GM.

I could see a GM argue that tremorsense can detect a creature before they jump and thus a creature could accurately predict how they will move through the air.

I could see a GM argue that tremorsense does not detect jumping creatures for exactly the same reasons that it does not detect flying creatures.

A small frame challenge I want to point out is the scenario happening at all; this would require the attacker knowing that the enemy has tremorsense, being in a Heavily Obscured area, and then successfully attacking while moving in mid-air. At least for me, that is no easy task. I have not personally dealt with mid-jump attacks so I'm unsure how I'd actually rule mid-session, but I imagine that I would require some sort of roll to determine whether the character can even pull this stunt off.

edited Nov 10 '20 at 02:07

answered Nov 09 '20 at 03:15

Exempt-Medic

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I would certainly rule that if a creature can sense your footsteps so well that they can tell exactly where you are, then they can also tell which way you're running and how fast. So a brief jump shouldn't make any difference, unless you have some way of changing your direction in midair. Most non-flying creatures don't. – Ilmari Karonen Nov 09 '20 at 03:24
@IlmariKaronen I think some of the problem would be that the jump might not be "brief"; in fact, it could be exceptionally long or remarkably high. Of course, there's also the weirdness of running out of movement mid-jump and other non-simulationist problems such as being able sprint in one direction and then jump in the exact opposite direction just as easily as jumping forward – Exempt-Medic Nov 09 '20 at 03:29
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Good point. As long as we're just talking about more or less normal mundane jumping within the context of the rules, presumably tremorsense ought to be enough to sense any last-footstep direction changes. After all, sensing footsteps is what it's good for. But if the player's jump was magically augmented or otherwise exceptional, I could certainly see myself ruling otherwise. – Ilmari Karonen Nov 09 '20 at 03:40
Of interesting note when looking through published monsters I haven't found any blind monsters with tremorsense. With only four exceptions (Borborygmos, Mantrap, Sacred Stone Monk, Stone Melder) they all have either have blindsight or darkvision. – Nov 09 '20 at 07:28
@IlmariKaronen: You're not accounting for the possibility of the jump beginning outside the range of tremorsense. If you have an attack with a range of 60', against an enemy with tremorsense of 60', and jump starting at 65' away, closing to within 60' mid-jump, their tremorsense never had a change to detect you. Obviously, this is a little silly from a real world perspective; perception generally isn't a binary state, so if you can detect tremors at 60', you should be able to sense them (if more dimly) at 65', but not being the real world, we can make silly arguments. :-) – ShadowRanger Nov 09 '20 at 18:31
First sentence typo? what we do not is that - I think was supposed to be "what we do know**"? – Peter Cordes Nov 10 '20 at 00:08
@IlmariKaronen: You think tremorsense would let a creature detect which direction you pushed off the ground in? Seems to me it could detect where that foot-strike was, and that it was harder than others, but in rigid stone it's unlikely to be a big difference between pushing somewhat left vs. somewhat right, and ending up at the end of a 10-foot-long jump attack either on the creature's right or left side, if the attacker had originally been running straight at the centre. That's not enough to help in dodging; the creature can't guess where the attack is coming from. – Peter Cordes Nov 10 '20 at 00:14

Mark Wells · Answer 2 · 2020-11-10T23:04:34.313

Tremorsense doesn't let you see.

Tremorsense is not described as a kind of vision (like darkvision and truesight), nor as a substitute for vision (like blindsight), nor is it named "vision" or "sight", nor is it listed in the Vision and Light rules. All signs point to it not being a vision-like sense.

It lets a creature sense the location of other creatures, but knowing a creature's location is different from seeing it, as implied by the Unseen Attackers and Targets rule:

When you attack a target that you can't see, you have disadvantage on the attack roll. This is true whether you're guessing the target's location or you're targeting a creature you can hear but not see.

That rule implies that you can't properly attack or defend with tremorsense against opponents who can actually see you. (This often won't matter. Creatures with tremorsense tend to be burrowers, and when you're burrowing, nobody can see anyone because it's dark and the soil is in the way, so tremorsense is very advantageous.)

So, can the creature with tremorsense detect the jumping guy in midair?

Suppose, for example, the ankheg had a readied action to burst out of the ground and attack when someone moved across its space. If Raflannan jumps completely over it, can it take its action?

Well, in one sense, trivially not. Tremorsense only works for things touching the ground. Raflannan is not touching the ground while moving through that space, therefore he is not detected.

On the other hand, it's a pretty obvious deduction. You're tremorsensing a sequence of footsteps approaching from one side. They speed up to a sprint, then there's one hard push, and then the footfalls stop. What do you think happened? Given that you can track their speed and direction right up to the big leap, you can probably guess exactly where they are (with the small risk of being faked out if they, say, caught hold of an overhanging tree branch, or cast misty step). At the table this may very well meet the requirement for a readied action trigger to be "perceivable", or allow attacking them with disadvantage if it's somehow your turn.

I suspect it's left out of "Vision and Light" rules because those rules were borrowed from the PHB, which didn't provide rules for tremorsense, or reference it in any way at all. It's included in Senses (which originates in the MM), and it may just be a matter of trying to simplify the PHB that caused it to be omitted from PHB rules. Not saying you're wrong, just that the evidence of "not in Vision and Light" isn't proving much. — ShadowRanger, Nov 09 '20 at 18:58
@ShadowRanger sure - but the Senses section just says that it lets you "detect and pinpoint the origin of vibrations". That's enough to let you know where the invisible guy is, so that you don't swing at an empty square, but you still get disadvantage. The Ankheg, for example, has both tremorsense and darksight. — Ben Barden, Nov 10 '20 at 03:01
It may be worth mentioning the difference between seeing a target and simply being aware of their location, as differentiated in the combat rules section on Unseen Attackers and Targets. — smbailey, Nov 10 '20 at 21:14

user-781943 · Answer 3 · 2020-11-11T02:35:12.703

Tremorsense can only detect vibrations that are in contact with the ground

A monster with tremorsense can detect and pinpoint the origin of vibrations within a specific radius, provided that the monster and the source of the vibrations are in contact with the same ground or substance.

While you are jumping you are not in contact with the ground, therefore you cannot be detected by tremorsense.

Tremorsense is not a kind of sight

The rules for vision are listed under the Vision and Sight section. The following types of vision are listed: normal vision, blindsight, dark vision, and truesight.

Tremorsense is listed in the Senses section which lists "special" senses. The methods of sight from above are listed, in addition to tremorsense. Other mundane senses are things like hearing, touch, taste, and smell.

There are various rules in 5e that only apply to sight, or apply to all senses, so keeping the concept of "sight" as a higher tier of senses will help you interpret rules - remember all "sights" are "senses", but not all "sense" are "sight".

Raflannan's attack is not at disadvantage, regardless if they jump or not

Raflannan is fighting an Ankheg in heavy fog. Neither can see each other. The Unseen Attackers and Targets rules govern this situation:

When you attack a target that you can't see, you have disadvantage on the attack roll.

When a creature can't see you, you have advantage on attack rolls against it.

Raflannan is attacking a creature they cannot see, so they have disadvantage. However, the Ankheg cannot see Raflannan so that means Raflannan gets advantage. Advantage and disadvantage cancel out, so it is a normal attack.

Other senses help you locate creatures

But hang on a second, what about tremorsense? Well, even in heavy fog you are still aware of everyone else's locations via your other senses - the Unseen Attackers and Targets rules even mention that: