Can invisibility be countered by "ramming" the whole room with lots of conjured animals?

Question

We're running Dragon Heist and having a quite dramatic encounter where a very important & powerful villain is trying to escape the sewers with 1 hp left.

The villain became invisible as the most logical first move and started to quietly go away towards the room's exit. The party screwed up a bit and didn't prepare ANY spells for invisibility detection, despite being at 6th lvl, not even the Faerie Fire. So the DM decided that it should be quite challenging for the party to stop that invisible villain from running away, without those spells.

But it turned out that the party wanted that guy dead SO MUCH, so they came up with an interesting move: summon 8 wolves with Conjure Animals and basically try to find the invisible enemy by bumping into it. The party literally spent some time drawing lots of "projectiles" in Roll20, trying to cover every square of the room with these "wolf ramming lines":

The DM decided that the villain, being a 17 lvl boss ranger, is not stupid and he will be trying to dodge the wolves by throwing a DC 15 acrobatics skill check. If succeeded, the wolves will not notice anyone on their way. And so the wolves missed because the villain had +8 to Acrobatics.

This actually made the party even more dedicated to kill that guy so the wolves started "dashing back and forth" through the room to maximize the number of potential acrobatics checks... They ended up killing the guy and may I say that was an extremely satisfying moment for the party :).

On the other hand, some of the players felt that DM was "giving the villain a plot armor" with this acrobatics checks ruling. They argued that this should be done differently via a Ready Action ("I jump away if a wolf tries to ram me"), or by wasting the action on Dodge, or with the DEX save, not the ability check...

Here are my questions:

1. According to the rules, is it really possible to do the "mass ramming" of an invisible enemy with a pack of wolves?

2. If this tactic is reasonable, what does the villain must do to counter it? Was the acrobatics check the most reasonable choice? Shouldn't it really be the Dodge action, or the Ready action, or the DEX save?

Answer 1

You know where the invisible creature is

Invisible is not hidden.

Your BBEG needed to become invisible and then take an action to hide. This would likely require 2 turns unless he had some way of either hiding or becoming invisible as a bonus action.

Even if hidden, the more perceptive of you might still know where he is

The BBEG hides and makes a Dexterity (Stealth) roll to see how well he did it. Any creature whose passive perception is as good or better still knows where he is.

Those who primarily rely on sight have disadvantage (-5) on their passive perception. Dire wolves have keen hearing and smell so they don’t primarily rely on sight. They also have a pretty decent passive perception of 13.

However, a 17th level ranger with max Dexterity will have +5 to Dexterity (Stealth) if not proficient and +10 if they are so they will probably successfully hide.

Searching

Searching is an action you can do during combat. It allows you to make an active Wisdom (Perception) check in order to find something. At first blush, this is what your wolves are doing.

This would be the way I would have played it rather than the way your DM did. That doesn’t make your DM wrong. Given the technique you employed, I would be more than happy to give your wolves advantage on their Wisdom (Perception) checks.

However, as stated the BBEG is likely to be good at hiding so the wolves still might not find him.

The rules do state that you can move through a non-hostile creature’s space. At this point the BBEG can be considered non-hostile in the sense that he would not be actively trying to hold his ground but rather carefully stepping aside as the wolves passed by. A 5x5 foot space is a big area, there’s plenty of room for man and wolf to share it without touching. If you ever played blind man’s bluff you will know just how hard it is to find someone you can’t see.

Rulings not rules

You came up with a plan and your DM came up with a way to resolve that plan. The DM does not have to make the “most reasonable” choice - that would be placing unreasonable expectations on them.

As I said, I would have ruled by projecting your plan onto the rules. In all likelihood this would be harder for you than the ruling your DM came up with. Would this be reasonable? Don’t know, don’t care m’lord - I’m a DM not a defendant in a trial.

Now, if you’d come up with a plan that involved a systematic sweep of the area with no gaps between searchers, then I might rule that you would automatically find the BBEG. Of course, that takes time to organise and the BBEG is unlikely to passively wait for you, he could be long gone before you start.

Answer 2

Yes, you can do a mass ramming, but it doesn't help as much as you hope

Let's look at the definition of the invisibile condition:

• An invisible creature is impossible to see without the aid of magic or a special sense. For the purpose of hiding, the creature is heavily obscured. The creature's location can be detected by any noise it makes or any tracks it leaves.
• Attack rolls against the creature have disadvantage, and the creature's attack rolls have advantage.

So there is a difference between being invisible and hiding. While invisible, they can still be detected unless they take steps to hide. But even if they don't, they are still invisible so you will still have disadvantage on your attacks.

If you look at the section on unseen targets:

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. If the target isn't in the location you targeted, you automatically miss, but the DM typically just says that the attack missed, not whether you guessed the target's location correctly.
When a creature can't see you, you have advantage on attack rolls against it. If you are hidden--both unseen and unheard--when you make an attack, you give away your location when the attack hits or misses.

So whether or not your villain is trying hide, and even if a bunch of wolves manage to bump into them, they are still invisible. You will know approximately where they are, but you'll still be at disadvantage. Your DM will likely rule that you won't automatically miss since you have a general idea.

As far as the DM ruling that the BBEG can dodge the wolves, that is a DM fiat call.

Technically, due to size, the wolves cannot pass through the BBEG space. But logic would say that the BBEG could allow it.

Answer 3

You can discover a hidden, invisible creature by running into it

The Invisible condition really only imparts these two effects (Conditions, PHB p. 291):

• An invisible creature is impossible to see without the aid of magic or a special sense. For the purpose of hiding, the creature is heavily obscured. The crea­ture’s location can be detected by any noise it makes or any tracks it leaves.
• Attack rolls against the creature have disadvantage, and the creature’s attack rolls have advantage.

So, just by becoming invisible, the ranger is not hidden from you. You can still hear where he is moving, unless he succeeds on a Dexterity (Stealth) check to hide from you, which he can do in plain sight, as he is invisible. Page 177 PHB:

An invisible creature can’t be seen, so it can always try to hide. Signs of its passage might still be noticed, however, and it still has to stay quiet.

With these rules in mind:

1. Can you detect an invisible creature by running into it, or having a wolf run into it and give a signal? Yes. The creature is not intangible. And running into an invisible obstacle will make you aware it is there.

2. What mechanism would be used to avoid being run into? There is no defined action for this, so how they handle it will be up to your DM.

To give some consideration to the options:

A Dexterity (Acrobatics) check seems reasonable, as the ranger is trying to dive out of the path of the wolf and the description says:

The DM might also call for a Dexterity (Acrobatics) check to see if you can perform acrobatic stunts, including dives, rolls, somersaults, and flips.

A Dexterity Saving throw seems to be less of a fit. The PHB says on page 180:

A saving throw—also called a save—represents an attempt to resist a spell, a trap, a poison, a disease, or a similar threat. You don’t normally decide to make a saving throw; you are forced to make one because your character or monster is at risk of harm.

The wolves bumping into them is not harming them, only the long term consequences are. And they are not being forced to, they are actively trying to avoid the wolf.

A Dodge Action is not a great fit. The wolves are not attacking the ranger, and the dodge actions purpose is to avoid attacks. It also gives advantage to Dexterity Saving throws, which we did treat above. PHB p. 192

When you take the Dodge action, you focus entirely on avoiding attacks.

The Ready Action is tricky. The ranger could save his action to ready moving out of the way, however the problem here is that the reaction happens after the trigger happened , so it is likely to be too late (PHB p. 193):

When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger.

To the DM could determine that the trigger is "the wolf is about to run into them, or running towards them and within a certain distance, which could work. Still, you only have one reaction per round, so you could avoid only a single wolf run.

Answer 4

Perception isn't just visual; it includes smell

The wolf has a passive perception score of 13 (see Wolf Stat Block in PHB, MM, or Basic Rules) and then there's this:

Keen Hearing and Smell. The wolf has advantage on Wisdom (Perception) checks that rely on hearing or smell

Turning invisible does not turn off one's smell. How any humanoid performs a "hide what I smell like" check is quite situational, but in the situation you describe the wolves would likely smell him, and if acting as a pack most likely attack with normal rolls (not disadvantage) since the pack tactics gives advantage to offset the disadvantage of the target being unseen. That said, if a lone wolf bumps into him the attack would be with disadvantage.

In further support for bump into him and attack, unallied creatures can't occupy another creature's space unless an exception (like some incorporeal creatures) is listed in the stat block, or the size difference is two or greater.

A creature’s space is the area in feet that it effectively controls in combat, not an expression of its physical dimensions. A typical Medium creature isn’t 5 feet wide, for example, but it does control a space that wide. If a Medium hobgoblin stands in a 5-­foot-­wide doorway, other creatures can’t get through unless the hobgoblin lets them.

With eight wolves following their noses, a few will bump into the Ranger unless the Ranger can move upwards and avoid being on the ground. They might still smell him, but they ay have difficulty with the jump and attack bit depending on the terrain. Some DM judgment is required in that case.

Another judgment call in this case is probably needed

Dodging or otherwise evading (such as using 14th level Ranger skill Vanish, which helps with the hide) could increase the difficulty, but is 'tracking' involved or Perception? They two seem to be mechanically different, so a DM ruling is needed for that.

Bottom Line: this was a good tactical use of the spell

The wolves should have found the ranger and been able to attack him, either with disadvantage if it was only one wolf, or both with normal rolls by use of pack tactics.

Answer 5

Question 1: According to the rules, yes...and very much yes.

Since you're playing on a grid, the rules are relatively clear on the matter of the space that a character can occupy as well as control:

A creature’s space is the area in feet that it effectively controls in combat, not an expression of its physical dimensions. A typical Medium creature isn’t 5 feet wide, for example, but it does control a space that wide. If a Medium hobgoblin stands in a 5-­foot-­wide doorway, other creatures can’t get through unless the hobgoblin lets them.

A creature’s space also reflects the area it needs to fight effectively. For that reason, there’s a limit to the number of creatures that can surround another creature in combat. Assuming Medium combatants, eight creatures can fit in a 5-­foot radius around another one. Because larger creatures take up more space, fewer of them can surround a creature. If five Large creatures crowd around a Medium or smaller one, there’s little room for anyone else. In contrast, as many as twenty Medium creatures can surround a Gargantuan one.

As you may notice from my emphasis, a creature can always let others through their space, which is what this opponent was ostensibly doing.

So overall, it's important to recognize that creature's in combat are not actually 5'x5'x5' cubes (except for when they are) and they can always allow others to move through their square. This is very common when player characters are in a narrow corridor and wish to allow each other to pass by one another so that they can take their turns.

So now lets get to the nitty gritty of what other rules are in play. First the rules on unseen targets:

Combatants often try to escape their foes' notice by hiding, casting the invisibility spell, or lurking in darkness.

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. If the target isn't in the location you targeted, you automatically miss, but the DM typically just says that the attack missed, not whether you guessed the target's location correctly.

When a creature can't see you, you have advantage on attack rolls against it. If you are hidden--both unseen and unheard--when you make an attack, you give away your location when the attack hits or misses.

Next, Acrobatics check:

Your Dexterity (Acrobatics) check covers your attempt to stay on your feet in a tricky situation, such as when you’re trying to run across a sheet of ice, balance on a tightrope, or stay upright on a rocking ship’s deck. The GM might also call for a Dexterity (Acrobatics) check to see if you can perform acrobatic stunts, including dives, rolls, somersaults, and flips.

I'd say that an invisible creature jumping out of the way of a bunch of wolves who are rushing at them fits the bill of an acrobatics check.

So for this DM, yes, this is fine per the rules.

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Question 2: Whatever the DM says they should do

This question, as phrased, is very subjective. 5e has a general mantra of rulings, not rules. And that mantra is most applicable here. Here's a list of various things which might be appropriate if I were the DM:

• Acrobatics check to avoid the wolves as they run past you (your DM's choice);
• Dexterity save against the caster's DC
• If the invisible character is trying to avoid detected on subsequent turns, they could take the Dodge action in order to grant themselves Advantage for the Dexterity save.
• Opposed Stealth versus Perception checks between the wolves and the ranger. The wolves would have Advantage on their rolls due the wolves' Keen Hearing and Smell.

From my perspective, none of these choices is wrong. They're all an answer to the same question.

I will state that your suggestion that the enemy ranger use the Dodge action or the Ready action don't feel correct to me based on the intended specific purpose of those rules.

Answer 6

This is a weird edge case in the rules.

Trying to treat a pack of wolves like a bag of flour in that it helps you spot an invisible, hiding creature by brushing off it as it moves through a coverless area (like an open tunnel) is an edge case in the hiding, invisibility, wolf, movement, and perception rules - it is not explicitly covered.

Thus whatever the DM comes up with is what the rules say to do. This is one of the reasons you have a DM in the first place.

All you can really ask for is does their response make sense? Mathematically, allowing movement to invalidate stealth check, hide action and invisibility, with no save, is not balanced. Movement is not meant to do that even if you can walk across all the floor. Stealth is not simply hiding under a bed, it's the entire process of concealing yourself from someone, including by flattening yourself against a wall as they go past etc.

Thematically, a super high level ranger should be able to deal with wolves. That's kind of their entire class theme, dealing with animals and the wilderness. They should be the best out of pretty much any class at doing so, and should not be discomfited by some summoned animals running about.

Likewise, a 17th level ranger should typically be a very dangerous encounter for a party of 6th level characters. An average 17th level ranger using tactics associated with their class (sniping, hiding, using spells to increase their damage or harass) is the kind of foe that could easily cause a TPK of a 6th level party, or at least force them to run away or take cover.

Therefore - to answer the question, can invisibility be countered by movement across tiles? Sure, in some situations, depending on DM rulings.

However, should it have countered invisibility in this situation? No. The ranger should have handily dealt with the wolves running around, or had a very good chance to, by virtue of being a high level ranger.

Since apparently the party was upset at the ranger even having a chance of escape, and handily defeated what should have been an extremely difficult encounter, the DM is likely making rulings that heavily favour the party and/or pulling punches or softballing in other respects, leading to a level of 'godmode' for the PCs. Under that circumstance, the ranger being found by whatever the party came up with is likely fine and part of the accepted milieu of the table.

However in general, no, a 17th level ranger should not have issues hiding from wolves, especially if they are invisible. If they are having issues hiding from wolves, that's pretty weird for a member of that class at that level and I (and many other people) would find that odd and unthematic (on top of not being supported by the rules).