D&D 5E Targetting total cover.

[MG.0]

Normally you cannot target something with total cover.

But there are situations where it might make sense to allow a ranged attack against a target with total cover. Imagine a group of monsters behind a high wall, but some distance away from it. A character on the opposite side wants to fire his bow in an arc over the wall. Presume he has some knowledge of where the targets are, e.g. a spotter on the wall, or having seen a target run behind the wall and assuming constant speed and direction. If we allow it, then obviously he can't see his opponent so at the least he would have disadvantage on the roll.

However I'm not sure if this would be any different than firing at an invisible opponent, or if an additional AC bonus is in order due to cover. My gut feeling is that if the character is unlikely to accidentally hit the wall with the arrow, then it isn't really providing cover, merely blocking line of sight.

 

[Shiroiken]

If you wanted to fire over a wall to hit someone behind it, I would rule that you have Disadvantage, and have to guess as to their specific space (just as if they were invisible). It shouldn't be easy, but not impossible either.

 

[ccooke]

Depends on the circumstance.

Simply having an archer predicting the path of the target is pure blind shooting, as standard - the archer aims for a square and has disadvantage. For a lofted shot over an obstacle, though, I might apply cover rules as well, or increase the AC. It would depend on the weather, too!

A spotter somehow telling (Message cantrip?) the archer where to shoot? This is essentially a knowledge transfer problem.
Here is how I've previously ruled in similar situations:

First, I assign a DC to explaining the situation. In this case, this is "How hard is it for the spotter to describe the shot the archer needs to make?". This will be used both for the spotter and the archer. Disadvantage if the spotter can't actually see the archer, of course. The players are, of course, not told the DC.
Then the spotter makes an Intelligence check against that DC and I record their margin of success (or failure!)
Finally, I ask the archer to make a Wisdom check to understand the instructions from the spotter. The spotter's margin of success is subtracted from the DC - so if the spotter did well, the check is easier. If they did badly, the DC increases.
(This is, effectively, the cooperative version of an opposed roll)

The archer then makes their shot using the blind shooting rules (I would probably treat this as the above simpler case). The cooperation roll determines whether the archer is aiming at the right spot or not - I would probably roll a d8 for direction and use the amount the roll failed to determine how far off course it is, for a failure.

That all looks quite complex in type. It seemed much simpler when improvising in play, somehow!

 

[Hand of Evil]

If the player does the math and shows me their work, yea I will allow it but with modifications to DC

 

[Hriston]

Indirect Fire

This is an issue not only of indirect fire, but that the target is unseen and therefore possibly hidden, so first I would need to determine if the the target was indeed hidden from the archer. To do this, I'd roll a stealth check for the target, maybe at advantage depending on the size of the intervening wall and the distance involved, and compare this with the archer's passive perception, possibly at disadvantage. If the target is hidden, of course, the archer will need to guess where the target is, and if s/he guesses wrong the attack will miss.

Assuming the archer guesses right, or that the target is not hidden, however, I'd modify a few things due to the use of indirect fire. First of all, I wouldn't impose disadvantage. The target is unseen (disadvantage), but so is the attacker from the target's point of view (advantage), so anything that gives advantage or disadvantage will be cancelled out by that circumstance. No one has the advantage here.

I would impose a range restriction. The target must be within long range of the archer's weapon, meaning out of short range. My assumption here is that short range represents a straight shot, whereas long range is accomplished with an arcing trajectory, thus the increased difficulty of the shot (represented by disadvantage, which I am not using due to the attacker being unseen). I'd shorten the range distances of the weapon, however, to 2/3 of their normal values because of the high angle being used to surmount the wall. For example, if the attack is made with a longbow, the target would need to be at least 100' away, but no more than 400' away. This is assuming the wall is roughly centered between the archer and the target.

I would also give the target the +2 bonus to AC for 1/2 cover because although an attack is possible due to the wall not protecting the target from an arrow coming from above, the high angle of the attack results in an effectively smaller target, roughly 1/2 the size.

 

[MG.0]

Lots of good ideas people.

Having the player point out the square isn't really possible in my games as we do not use miniatures or a map. This does complicate things a bit because I have to somehow generate the probability the archer is shooting in the right direction. If he has a spotter, or other indirect knowledge I assume he fires in the correct general direction and make it a disadvantaged attack. Lacking that knowledge woud impose an additional penalty. I generally just 'wing it' with regard to the penalty based on circumstance as there seem to be no clear rules for it when not playing with a grid.

Hriston's idea of negating the disadvantage because the attacker is unseen makes sense from a rules perspective, but feels wrong for some reason I can't quite specify. I'm not sure I would alter the range of a bow for shooting over a wall, as shooting at long range involves firing at a higher angle anyway. My first thought was to disallow shooting at targets closer to the wall than the archer is, but a highly arced could hit someone in that situation, although my gut says that kind of attack would be harder to pull off.

 

[thalmin]

The target might not see the attacker, but could possibly see the arrows incoming, and therefore should be able to react. I would definitely impose disadvantage to the attack, along with other adjustments.
YMMV

 

[Jester David]

I'd give the enemies the benefit of cover (AC bonus) while also imposing disadvantage on the attacker.
I'd also have the character pick an area behind the cover they're attacking and *think* the creature is (since they can't see) and attack that space rather than the creature. If they pick the wrong area, auto miss.

 

[Quartz]

Funnily enough I was thinking about a similar situation earlier today: when you want to fire through the cover. For example, throwing a spear through a door. Obviously you've got to do enough damage to penetrate the object, which might be 1 hp for a paper wall or a glass window to lots for a granite wall. And a perception roll might be necessary to learn your target's location - not necessary for being the other side of a glass window, of course, but something along the lines of, "The light from beneath the door shows you that something is standing right behind it."

 

[Treantmonklvl20]

I would say 3/4 cover + disadvantage. Super-hard but technically possible. This is only if the player can provide me with a reasonable method they are using to have their attack circumvent the cover (as in the example you provide). This is worse than just not seeing your target - there is an obstacle you need to avoid as well, and you will need to angle your shot just right. That shouldn't be easy.