Firing through invisible creatures

[Gungor]

Suppose that there is an invisible creature directly between you and a target you are trying to hit with a ranged weapon. Let's say an arrow to be concrete. Suppose also that you are unaware of the presence of the invisible creature. In "real life" I'd expect there's some chance you would hit the invisible creature instead of your target. Do the RAW give any insight into how to adjudicate this in-game?

Some thoughts I have on how I might adjudicate it, are:

1. Roll an attack against the invisible creature (with disadvantage as usual). If it happens to hit, then you hit the invisible creature. If not, then roll the attack against the target as normal. Two major downsides to this are, depending on how you implement it, you might signal to the player that there's something fishy going on. More importantly, you have disadvantage attacking an invisible creature when that is what you are trying to do, and when you have some idea where to aim. It seems like the chance of hitting should be even less in this circumstance.

2. Roll the attack against the target but give it partial cover. If the attack misses, but would have hit without the cover bonus, describe how the arrow seems to have been deflected/stopped in mid-flight, to signal that it contacted the invisible creature providing the cover. The downside to this approach is that the way I think of it, the reason why cover gives a bonus to AC is because you are trying to aim at what's exposed. This is why when a visible ally provides cover, you don't accidentally hit them with the attack. It seems like you are more likely to aim at a "covered" part that you are unaware of. Is the answer to award a higher category of cover?

3. Kind of a mash up of 1 and 2 - impose disadvantage on the attack against the target. If the attack misses but the higher roll would have hit, describe the arrow as having been deflected/stopped as above. An advantage to this approach is that there is no "tell" - just say "roll with disadvantage" or even "roll 2d20". It is probably the simplest rule to implement as well.

As with all rules the goal is to balance realism with simplicity. To take this example to a ridiculous extreme, suppose there is an invisible Purple Worm between you and your target. By any sensible definition, that target has total cover, but you don't know it. And any attempt to shoot an arrow at the target is either going to hit (i.e. damage) the Purple Worm, or will bounce harmlessly off of its hide (to you, it looks like the arrow bounced off of an invisible wall).

[CorporateSlave]

2. Roll the attack against the target but give it partial cover. If the attack misses, but would have hit without the cover bonus, describe how the arrow seems to have been deflected/stopped in mid-flight, to signal that it contacted the invisible creature providing the cover. The downside to this approach is that the way I think of it, the reason why cover gives a bonus to AC is because you are trying to aim at what's exposed. This is why when a visible ally provides cover, you don't accidentally hit them with the attack. It seems like you are more likely to aim at a "covered" part that you are unaware of. Is the answer to award a higher category of cover?

Probably pretty much this one, using the optional "Hitting Cover" rules from the DMG:

"When a ranged attack misses a target that has cover, you can use this optional rule to determine whether the cover was struck by the attack.

First, determine whether the attack roll would have hit the protected target without the cover. If the attack roll falls within a range low enough to miss the target but high enough to strike the target if there had been no cover, the object used for cover is struck. If a creature is providing cover for the missed creature and the attack roll exceeds the AC of the covering creature, the covering creature is hit."

If the "miss" due to the invisible "cover" would not break the invisible creature's AC, then the arrow could be described as deflecting. If it would otherwise hit the invisible AC, then it should stick (and deal damage)!

I would adjudicate in this way even with the "purple worm" situation, based on the principle that a creature doesn't ever really occupy the full space of it's grid "footprint", and during combat everyone is constantly shifting around. A moving purple worm doesn't necessarily provide full cover if it is invisible and the covered creature can't see where to move with it to maintain the break in LOS, imho.

[Keravath]

As mentioned there is the optional rule in the DMG for hitting cover. This is mostly intended for ranged attacks into melee where other creatures are providing the cover but can easily be extended to invisible obstacles/creatures or other obstructions.

In the case of invisible total cover, you would just describe the ranged weapon attack as hitting something before reaching the target. This could be an invisible purple worm or a wall of force that the character does not know about. Either could provide total cover for weapon attacks.

It is an open debate as to whether invisible or transparent obstacles (invisible creature/object, wall of force, window) provide total cover for spell attacks (if they provide total cover then you can't actually even target the creature behind the transparent obstacle) unless those attacks are described as passing through the space from the caster to the target.


e.g. eldritch blast or firebolt are both described as energy traveling from the caster to the target and could be blocked if there was something invisbile in their way, on the other hand chill touch is described as creating a ghostly hand next to a target within range and then rolling a ranged spell attack. It doesn't say anything about the space between the caster and the target.

However, if the transparent obstruction provides total cover then the DM has to tell the player that they can't cast the spell because even though they can clearly see the target it has total cover which immediately tells the player that there is something they can't see between them and the target.

[willdaBEAST]

Barring a large creature, I would personally avoid complicating the mechanics. A normal sized humanoid would also probably react to someone taking aim directly at them. If the goal is to subtly reveal the invis creature, I would either go off of passive perception or have a perception check to see if the PC hears something unusual as the invis enemy avoids being shot.

[CorporateSlave]

Barring a large creature, I would personally avoid complicating the mechanics. A normal sized humanoid would also probably react to someone taking aim directly at them. If the goal is to subtly reveal the invis creature, I would either go off of passive perception or have a perception check to see if the PC hears something unusual as the invis enemy avoids being shot.

Based on the OP's description of the scenario, the implication is that the Invisible creature is also Hidden from the attacker (i.e. already beaten Passive Perception with Stealth). The Hitting Cover rules are pretty simple, the attacker still makes the Attack with just a single d20 roll, but with a modifier (which would be used regardless) but two AC's to compare the result to.

Just because a creature has a Large footprint, I would almost never rule it grants Total Cover in a combat situation - if for no other reason than it takes away from a Halfling's racial ability to Hide behind a creature at least one size larger (if a larger creature provides full cover from Attacks, why should it not also provide Heavy Obscurement for Hiding to anyone/anything?) You're ruling whatever is behind it cannot be seen at all!

I think of it this way - a horse is a Large creature. If there is a horse between an attacker and their target, is there literally no way an attack could bypass the area the horse is standing and strike the target? Of course it could, maybe below the head, over the back, between the legs, etc. But it would be harder to hit because you're trying not to hit the horse, and if you miss, it might hit the horse instead. So if the horse is Invisible, the shot may still go through (a high d20 roll would just mean narratively that when the shot was loosed, it happened to have a trajectory that went unknowingly between the Invisible horse's legs, for example), but if it misses it may well strike the horse instead.

[Maelynn]

Looking at the other replies I'm probably thinking way too simple, but here's what I would do:

- player rolls attack, supposedly against visible enemy AC
- I secretly put invisible enemy's AC against it
- if hit: describe how the arrow suddenly stops mid-air and a yelp of pain is heard (possibly leading to enemy no longer invisible, depending on source)
- if miss, choose from one of these options:

-> if ricochet off metal armour: describe how arrow changes course with a barely audible 'chink'

-> if stuck in armour/skin without dealing damage: describe how the arrow suddenly stops mid-air

-> if flying over/past invisible creature, perhaps because it dodges: check against visible enemy AC, if hit then describe how the arrow flies true and hits intended target (player is unaware of invisible enemy)