Threatened areas and Cover

[Rukelnikov]

So, lets say creature A has 5ft reach, and creature B is right next to it.

If creature B backs away 5 ft it'd be leaving the A's threatened area, and thus provoking an AoO.

Now, what if B moves to a square that is within 5 ft of A, but that provides total cover from A, would this count as leaving the threatened area and incurr in AoO, or not?

[solidork]

This has come up in our games with Ghosts who phase through walls - our logic was that by the time it provokes the attack of opportunity it's completely inside the wall, so you can't make one.

[Rukelnikov]

This has come up in our games with Ghosts who phase through walls - our logic was that by the time it provokes the attack of opportunity it's completely inside the wall, so you can't make one.

That was exactly the interaction that provoked the thought, we've always ran it that they don't provoke for phasing below the floor, but just now did I stop to think whether that would count as leaving threatened area or not.

[Reynaert]

I think, RAW, you would get an attack of opportunity. "The attack occurs right before the creature leaves your reach", i.e. right before it moves behind (or into) cover.

Also I think that attacks of opportunity should have been worded the other way around: If an opponent moves in a way that puts you out of its reach, you get an attack of opportunity.

[stoutstien]

One of the many reasons OAs triggering when leaving reach is a dumb design choice.

[Rukelnikov]

One of the many reasons OAs triggering when leaving reach is a dumb design choice.

If moving withing an enemy's threatened area provoked, then battles would be completely static, with characters glueing to each other to not generate.

3e had this problem too, but used the 5 ft step to sidestep it (ba dum tish). The removal of the 5 ft step necessitated the change in how provoking works. IDR how it worked in 4e.

[Tes]

Looking at RAW for AOO (what Reynaert said) the AOO happens in the space that's in your reach.
Sentinel backs that up, since the creature doesn't get rooted after leaving, but before. And Sentinel only prevents disengage from working, doesn't change the trigger condition or anything else in this case "Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your reach".
So leaving into a Total Cover tile should still trigger AOO as normal.

The wording in the rules isn't great though.

[Rukelnikov]

Looking at RAW for AOO (what Reynaert said) the AOO happens in the space that's in your reach.
Sentinel backs that up, since the creature doesn't get rooted after leaving, but before. And Sentinel only prevents disengage from working, doesn't change the trigger condition or anything else in this case "Creatures provoke opportunity attacks from you even if they take the Disengage action before leaving your reach".
So leaving into a Total Cover tile should still trigger AOO as normal.

The wording in the rules isn't great though.

Right, if they move outside of your reach, they would trigger, but what if they move still within your reach?

Imagine combatant A is in D4, and Combatant B is in D5, B moves to E5, and doesn't provoke because they are still within A's reach.

But what if there's a 6 inch wall between the D and E files? Should it now provoke? Why?

[stoutstien]

If moving withing an enemy's threatened area provoked, then battles would be completely static, with characters glueing to each other to not generate.

3e had this problem too, but used the 5 ft step to sidestep it (ba dum tish). The removal of the 5 ft step necessitated the change in how provoking works. IDR how it worked in 4e.

OAs have little impact on how static or dangerous a challenge feels. Being in melee or not is not impactful for most PCs or NPCs to be a factor or if it is they don't rely on standard movement to address it.

Movement is messed up across the board so there rarely any built in reasons to move more than to engage/disengage (general terms not game) and OAs make this worse with adding on punishment for doing so by normal means.
I think there are more reactions that happen before the trigger than not, which is just a messed up way of dealing with it. You end up with a bunch of rules that works because they say so not because they make sense. This always leads to weird interactions that are nonsense.

[Reynaert]

Right, if they move outside of your reach, they would trigger, but what if they move still within your reach?

Imagine combatant A is in D4, and Combatant B is in D5, B moves to E5, and doesn't provoke because they are still within A's reach.

But what if there's a 6 inch wall between the D and E files? Should it now provoke? Why?

It all depends on what 'within reach' means. In plain language, the light switch on the other side of the wall I'm sitting next to, while certainly within two feet of me, is not within my reach.

Also, (take this with as many grains of salt as needed), JC tweeted that "Your melee reach does not extend into the wall or floor."

[Reynaert]

OAs have little impact on how static or dangerous a challenge feels. Being in melee or not is not impactful for most PCs or NPCs to be a factor or if it is they don't rely on standard movement to address it.

Movement is messed up across the board so there rarely any built in reasons to move more than to engage/disengage (general terms not game) and OAs make this worse with adding on punishment for doing so by normal means.
I think there are more reactions that happen before the trigger than not, which is just a messed up way of dealing with it. You end up with a bunch of rules that works because they say so not because they make sense. This always leads to weird interactions that are nonsense.

I believe OAs were added as a means to prevent gamist combat tactics like kiting, (maybe also as a way to slow down or stop attackers from breaking through lines). Unfortunately it's a very gamist rule by itself. (A lot of which is brought on by the way the goal of in game combat is often 'kill the other guys', unlike real-world where that is hardly ever the goal).

[Greywander]

My take is that they're still within reach, so no OA. Because they're now behind full cover, they can't be seen, so no OA if they now move out of reach, even if they can be seen in their new space. Being behind full cover also prevents them from being targeted by most effects, even those that don't require sight.

I'd understand if a DM wanted to rule this differently. OAs are one of those rules that don't necessarily make a lot of sense from a verisimilitude perspective and is mostly a game abstraction, so any implementation should be fine as long as it makes the gameplay more fun and interesting. Obviously, one of the 5e devs didn't like how static AoO made 3e, and so thought doing it this way would be more fun, and not everyone will agree about that.

I'd kind of like to see some kind of implementation of OAs that applies to ranged weapons, but that's going to be tricky to do without being overpowered.

[Tes]

Right, if they move outside of your reach, they would trigger, but what if they move still within your reach?

Imagine combatant A is in D4, and Combatant B is in D5, B moves to E5, and doesn't provoke because they are still within A's reach.

But what if there's a 6 inch wall between the D and E files? Should it now provoke? Why?

Then you're asking what "leaving reach" is. If a Fighter is with his back to the wall with a ghost on his right and that Ghost then decides to enter the wall, which is Total Cover.
Now is that Ghost inside the wall still withing reach, or did it just leave reach and would still trigger an AOO all the same?

I don't think there's a straight up answer here and it's pretty much up to your DM.
Personally I'd go by this
"Used in hand--to--hand Combat, a melee Attack allows you to Attack a foe within your reach".
If you can attack something with a melee weapon it is in your reach. If you can't attack it with a melee weapon it isn't.
There are things, mostly total cover that reduce the area covered by your reach. Another example would be something 2 tiles away within 10 feet, but around a corner, or two tiles away but on the other side of a wall.
"Your reach" as far as I am reading it is only the area you can literally reach with your weapon, tiles obstructed by total cover are not counted as within your reach.

So leaving the reduced area, would still trigger AOOs. Otherwise stuff breaks. You could negate the AOO for PAM with a polearm by abusing a corner to enter line sight and leave total cover from a starting position inside 10 feet etc.

[firelistener]

Is this confusing people because of how your DM runs it? Like when I have a monster leave a player's threatened area, I will say something like, "After bandit missed his attack, he starts moving to duck behind this wall. Would you like to make an attack of opportunity?" (Yes! I love attacks of opportunity! I rolled a 19!) "Okay, you manage to hit him right as you see him turn to leave, and he ducks behind the wall, now wounded."

I narrate the attack as ocurring before the movement really occurs. The attack is supposed to happen as the enemy leaves, not after. So a ghost moving through the floor or wall works the same way. They start to move out of your range, and you might get an attack in right before it slips away.

[Rukelnikov]

Is this confusing people because of how your DM runs it? Like when I have a monster leave a player's threatened area, I will say something like, "After bandit missed his attack, he starts moving to duck behind this wall. Would you like to make an attack of opportunity?" (Yes! I love attacks of opportunity! I rolled a 19!) "Okay, you manage to hit him right as you see him turn to leave, and he ducks behind the wall, now wounded."

I narrate the attack as ocurring before the movement really occurs. The attack is supposed to happen as the enemy leaves, not after. So a ghost moving through the floor or wall works the same way. They start to move out of your range, and you might get an attack in right before it slips away.

Right, but if the wall wasn't there the ghost wouldn't provoke, and its moving in the exact same way, so why there being a wall somehow creates an opening for the warrior?

[Reynaert]

Right, but if the wall wasn't there the ghost wouldn't provoke, and its moving in the exact same way, so why there being a wall somehow creates an opening for the warrior?

This is an edge case where the warrior is still in reach of the ghost, but the ghost is out of reach of the warrior. Strange things happen in edge cases, that's always a thing with rules as written.

Normally, when a warrior moves to cover behind a thin wall from another warrior (still within 5ft), both warriors would be out of reach from each other and an opportunity attack wouldn't be strange.

If you want to explain the ghost case narratively, let's say it needs to do something special to go through the wall (it can't end its movement inside the wall without taking damage, after all, so there has to be some effort going on), and that triggers the AoO.

[firelistener]

Right, but if the wall wasn't there the ghost wouldn't provoke, and its moving in the exact same way, so why there being a wall somehow creates an opening for the warrior?

The way I always explain and narrate AoO is that the combatant leaving takes their focus off of the other combatant to do so. So for with the ghost example specifically, I would say something like, "The ghost turns its attention to your ally nearby, and slips away through the wall to go attack them. You can sieze this opening to make an attack of opportunity right before it phases through the wall and out of your range." Or instead of attacking your ally, just whatever Action the ghost intends to commit. And the reason I know the ghost MUST have some other action it is going to take and is therefore focused on? It's not taking Disengage. Disengage exists solely for this reason. If the ghost were to Disengage, I would say, "The ghost phases through the wall, out of your reach, and takes the Disengage action before doing so, as it focuses on evading you while it passes through the wall."

So I don't see the ghost thing or any kind of cover as an exception or "moving in the same way" for that reason. It is the lack of focus on Disengaging that really leads to the "opportunity" for an attack.

[Tanarii]

I can't find anything that says reach doesn't extend through cover in the making an attack section under melee, which is where it is defined. Nor under cover, where all it says is creatures behind cover can't be targeted.

So IMO the wall vs non wall doesn't make a difference to provoking.

Edit: it's possible the option grid rules in the DMG work differently tho

[Kane0]

So, lets say creature A has 5ft reach, and creature B is right next to it.

If creature B backs away 5 ft it'd be leaving the A's threatened area, and thus provoking an AoO.

Now, what if B moves to a square that is within 5 ft of A, but that provides total cover from A, would this count as leaving the threatened area and incurr in AoO, or not?

I too have seen incorporeal creatures on both sides of the DM screen, and I think phasing and through solid obstacles in order to avoid taking OAs is part of their thing. I usually do it via the floor because that's my style, but walls are perfectly acceptable too.

That said, OAs are typically made at/from the spot they are leaving and not the new spot out of your reach, because that's what you still have reach to (and you don't move as part of the OA unless you're a Vengeance pally). Well for my table at least.

[Rukelnikov]

I can't find anything that says reach doesn't extend through cover in the making an attack section under melee, which is where it is defined. Nor under cover, where all it says is creatures behind cover can't be targeted.

So IMO the wall vs non wall doesn't make a difference to provoking.

Edit: it's possible the option grid rules in the DMG work differently tho


I too have seen incorporeal creatures on both sides of the DM screen, and I think phasing and through solid obstacles in order to avoid taking OAs is part of their thing. I usually do it via the floor because that's my style, but walls are perfectly acceptable too.

That said, OAs are typically made at/from the spot they are leaving and not the new spot out of your reach, because that's what you still have reach to (and you don't move as part of the OA unless you're a Vengeance pally). Well for my table at least.

This is my reading too, but wanted to see what other people thought about it.

[Reynaert]

I can't find anything that says reach doesn't extend through cover in the making an attack section under melee, which is where it is defined. Nor under cover, where all it says is creatures behind cover can't be targeted.

So IMO the wall vs non wall doesn't make a difference to provoking.

Edit: it's possible the option grid rules in the DMG work differently tho

I can't find anything that says reach does extend through cover, either. So we're stuck with the english language definition of the words 'out of your reach' in relation to walls inbetween the subject and object, which is debatable at best.

For example: If you're sitting in an office cubicle and there is a coffee mug in the next cubicle(*), is that coffee mug within your reach ?

*) Within three feet obviously, otherwise the question wouldn't make sense. Say, you and the coffee mug are both right next to the cubicle wall.

[Rukelnikov]

I can't find anything that says reach does extend through cover, either. So we're stuck with the english language definition of the words 'out of your reach' in relation to walls inbetween the subject and object, which is debatable at best.

For example: If you're sitting in an office cubicle and there is a coffee mug in the next cubicle(*), is that coffee mug within your reach ?

*) Within three feet obviously, otherwise the question wouldn't make sense. Say, you and the coffee mug are both right next to the cubicle wall.

I think Reach is a game term, not plain english, but I'm not really sure.

[RSP]

I think Reach is a game term, not plain english, but I'm not really sure.

When used in the combat rules, I believe it’s common English. When used as the weapon property it’s a game term.

[Segev]

Personally, I would probably allow use of terrain and obstructions to prevent OAs as long as you'd be in reach if the obstruction providing cover weren't there.

For example, if Bob the Bard is right next to Oscar the Ogre, and Bob simply moves five feet away from Oscar, Oscar obviously gets an OA. If Bob had 1/2 cover from a half-standing wall that Oscar had battered down last turn, Bob would benefit from that 1/2 cover's +2 AC when Oscar makes the OA against Bob as Bob moves out of Oscar's reach.

If Bob had no such cover where he started, but moved - still within Oscar's reach - to where such half cover existed before moving out of Oscar's reach, Bob still gets +2 AC vs. that OA. This is not in question; the rules interactions are definite, here.

Now, does this change if Bob moves from no cover to full cover without leaving Oscar's reach? Can he do that, or does getting behind full cover mean he leaves Oscar's reach? I don't think it does; somebody with full cover is unable to be targeted, but that doesn't mean he's out of reach/range. So I think that if you stay within reach distance, even if you move to a position with full cover, you're okay.

Which means that the ghosts do not provoke OAs if they descend into the ground or into a wall adjacent to the person threatening the OA and don't leave his reach.

Similarly, if there's a five foot cube of total obscurement (perhaps from the summon fey Fey Spirit having teleported there to make the block of darkness) within Oscar the ogre's reach, and Bob moves to that square before moving away from Oscar, the fact that Oscar can't see him means Oscar can't make an OA. Oscar doesn't get to make an OA just because he's losing sight of Bob when Bob enters the 5 foot cube of darkness; the cube is within Oscar's reach.

[Tanarii]

If Bob had no such cover where he started, but moved - still within Oscar's reach - to where such half cover existed before moving out of Oscar's reach, Bob still gets +2 AC vs. that OA. This is not in question; the rules interactions are definite, here.
Uh, no. Bob definitely does not get the AC bonus in that case. The OA happens before Bob is behind the half cover, since it happens before leaving the reach (and thus not in half cover), not after (and thus in half cover).

Oh jeez yeah strike that before coffee failure to read comment. :smallamused: Okay that's a good way to show the analogy, yes if you move within reach not provoking an AO so you're behind half cover, then move out of reach, Bob definitely gets the half cover bonus.

[Reynaert]

... Can he do that, or does getting behind full cover mean he leaves Oscar's reach? I don't think it does; somebody with full cover is unable to be targeted, but that doesn't mean he's out of reach/range. ...

This is the whole point of contention. I (and I believe almost everyone) agrees on the rest of your reasoning.

[Aimeryan]

I do believe most of this results from the turn-by-turn nature and the lack of facing. If the game had facing rules and play was phased then you could have a situation where backing up would be slower than moving forward, which would result in the need to turn around to move away from an opponent of similar speed attempting to stick with you, which would result in an opportunistic attack.

5e attempts to simulate this by presuming that leaving reach required this, therefore opportunistic attack. However, if you can move significantly faster than the opponent or move through things they cannot then it no longer makes sense since you wouldn't present that opportunity.

Does leaving reach having a defined state? If the reference is to the weapon properties then yes (distance alone). If the reference is plain english then yes (by any means which you could no longer reach with an attack, including full cover). Do we know which it is? Not really. Does either make more sense for the simulation? Well, neither is particularly good at simulating the opportunity presented, however, slipping behind cover or through an object the opponent cannot should be less of an opportunity for the opponent, not more. So, by means of elimination, the distance based version of the weapon Reach property is superior and I would go with that.

[Segev]

This is the whole point of contention. I (and I believe almost everyone) agrees on the rest of your reasoning.

Let's say Oscar is manning a ticket booth. One side (to his right, let's say) is completely open. The side in front of him and the side to his left have countertops with walls below them. The side behind him is a complete wall leading to the roof of the booth.

I would argue that, if Bob can start on Oscar's right and move around to Oscar's front without provoking an OA, he can move in exactly the same way around to Oscar's rear without leaving himself any more open. If he moves to Oscar's front, he would have half cover from any attack Oscar made at him. If he moves to Oscar's rear, he has full cover.

I understand that "does moving to full cover count as provoking an OA" is the whole question of the thread; I am suggesting that the answer lies in what happens if you move behind any other kind of cover, and how it shouldn't matter what kind of cover you move behind to determine whether you leave yourself open to the OA. Assuming that the only difference is whether Bob moves to Bob's own left or right around Oscar, what is the difference between moving to the front of Oscar or to the back of Oscar in terms of leaving himself open? Moving directly away from Oscar while Bob is on Oscar's right would leave him open, presumably because he is turning around and jogging; if he backs away carefully, obviously, that's the Disengage action. But moving around Oscar is presumed to require no extra movement and still not leave Bob open. I don't see why Bob would need to drop his guard and expose himself to attack to move one direction around Oscar and not the other, just because one direction has a higher wall.

[Keltest]

Let's say Oscar is manning a ticket booth. One side (to his right, let's say) is completely open. The side in front of him and the side to his left have countertops with walls below them. The side behind him is a complete wall leading to the roof of the booth.

I would argue that, if Bob can start on Oscar's right and move around to Oscar's front without provoking an OA, he can move in exactly the same way around to Oscar's rear without leaving himself any more open. If he moves to Oscar's front, he would have half cover from any attack Oscar made at him. If he moves to Oscar's rear, he has full cover.

I understand that "does moving to full cover count as provoking an OA" is the whole question of the thread; I am suggesting that the answer lies in what happens if you move behind any other kind of cover, and how it shouldn't matter what kind of cover you move behind to determine whether you leave yourself open to the OA. Assuming that the only difference is whether Bob moves to Bob's own left or right around Oscar, what is the difference between moving to the front of Oscar or to the back of Oscar in terms of leaving himself open? Moving directly away from Oscar while Bob is on Oscar's right would leave him open, presumably because he is turning around and jogging; if he backs away carefully, obviously, that's the Disengage action. But moving around Oscar is presumed to require no extra movement and still not leave Bob open. I don't see why Bob would need to drop his guard and expose himself to attack to move one direction around Oscar and not the other, just because one direction has a higher wall.

This is about where I sit as well. Let the ghosts and whatnot have some more tactical options. Its not like 5e is exactly overflowing with different creature combat strategies to begin with. And if somebody has Psychic Lance, War Caster and knows the name of the ghost, let them get the spell off. They can feel clever for being prepared.

[Reynaert]

Let's say Oscar is manning a ticket booth. One side (to his right, let's say) is completely open. The side in front of him and the side to his left have countertops with walls below them. The side behind him is a complete wall leading to the roof of the booth.

I would argue that, if Bob can start on Oscar's right and move around to Oscar's front without provoking an OA, he can move in exactly the same way around to Oscar's rear without leaving himself any more open. If he moves to Oscar's front, he would have half cover from any attack Oscar made at him. If he moves to Oscar's rear, he has full cover.

I understand that "does moving to full cover count as provoking an OA" is the whole question of the thread; I am suggesting that the answer lies in what happens if you move behind any other kind of cover, and how it shouldn't matter what kind of cover you move behind to determine whether you leave yourself open to the OA. Assuming that the only difference is whether Bob moves to Bob's own left or right around Oscar, what is the difference between moving to the front of Oscar or to the back of Oscar in terms of leaving himself open? Moving directly away from Oscar while Bob is on Oscar's right would leave him open, presumably because he is turning around and jogging; if he backs away carefully, obviously, that's the Disengage action. But moving around Oscar is presumed to require no extra movement and still not leave Bob open. I don't see why Bob would need to drop his guard and expose himself to attack to move one direction around Oscar and not the other, just because one direction has a higher wall.

I understand your reasoning, and it's quite sound. The thing, however, is that D&D at its core is very gamist, and you're using simulationist reasoning, which is where it clashes. I was arguing from a gamist perspective here, which I feel I should point out mainly because there is a mix of both forms of arguments in this thread which really muddies the waters.

Of course, I could probably come up with a quite plausible narrative reason why moving to the back in this scenario would, in fact, leave Oscar open to an oppority attack. It all depends on the exact narrative reason why you should get an opportunity attack for someone leaving your reach in the first place. But that's not the point and also I'd be going into the 'think too mu.

Basically what I'm trying to say is there are dozens of situations that are really weird if you follow D&D rules, if you think about it too much. And this feels, to me, like just another one of those situations.

Of course, giving characters the opportunity to avoid opportunity attacks by using cover has undeniable benefits and can certainly enhance your game.
Just be prepared to grant more such opportunities for different but similar situations, where the rules are just as unrealistic or too gamist.
(To be honest, we do that too in our games, though the thing about cover and AoO hasn't come up yet.)

[Aimeryan]

I understand your reasoning, and it's quite sound. The thing, however, is that D&D at its core is very gamist, and you're using simulationist reasoning, which is where it clashes. I was arguing from a gamist perspective here, which I feel I should point out mainly because there is a mix of both forms of arguments in this thread which really muddies the waters.

The issue here is that the rule is unclear - it is not more gamist to use either rule. All that is left is trying to guess what is being simulated by the rule and what makes greater narrative sense in general. The one that does this is the one based on the reach of an entity as being the distance only - i.e., not including full cover.

When you only go by distance, then moving behind full cover while maintaining that distance would not provoke an OA.

[Reynaert]

The issue here is that the rule is unclear - it is not more gamist to use either rule. All that is left is trying to guess what is being simulated by the rule and what makes greater narrative sense in general. The one that does this is the one based on the reach of an entity as being the distance only - i.e., not including full cover.

When you only go by distance, then moving behind full cover while maintaining that distance would not provoke an OA.

The issue here is that the rule is completely clear to me. It's why I keep hammering on about light switches and mugs in cubicles.
I simply can't fathom anybody seriously saying "Is there mug within your reach?" "Yes." "Can you grab it for me?" "No, there is a wall in the way."

[Aimeryan]

The issue here is that the rule is completely clear to me. It's why I keep hammering on about light switches and mugs in cubicles.
I simply can't fathom anybody seriously saying "Is there mug within your reach?" "Yes." "Can you grab it for me?" "No, there is a wall in the way."

It is unclear because reach is not keyworded - so the meaning of reach whenever it is used can be ambiguous as to whether it is meant to be how 5e appears to use it or as it means in common English. In any of the multitude of rules in which reach appears in 5e, only distance appears to be considered - cover is never mentioned. It would seem likely that if cover was meant to be considered when it came to reach it would have been mentioned at least once as to how it relates.

The problem with using reach as meant by common English in 5e is that it leads to less natural consequences in 5e - using cover shouldn't make you more vulnerable. When something is ambiguous just use the one that leads to better results and be consistent about it.

[Reynaert]

It is unclear because reach is not keyworded - so the meaning of reach whenever it is used can be ambiguous as to whether it is meant to be how 5e appears to use it or as it means in common English. In any of the multitude of rules in which reach appears in 5e, only distance appears to be considered - cover is never mentioned. It would seem likely that if cover was meant to be considered when it came to reach it would have been mentioned at least once as to how it relates.

The problem with using reach as meant by common English in 5e is that it leads to less natural consequences in 5e - using cover shouldn't make you more vulnerable. When something is ambiguous just use the one that leads to better results and be consistent about it.

First of all, the common English usage is not ambiguous at all. Normally (in 5e), either a game term is defined as a game term, or its usage is common English.
The only reason ambiguity is being introduced is because the consequences feel "less natural" to some people. So this feels a lot like circular reasoning.

Second, the term reach is used in the description of total cover, saying that "some spells can reach such a target", implying that normally an attack or a spell can not "reach" such a target. So that is arguably the "mentioned at least once" you wanted.

Third, "using cover shouldn't make you more vulnerable" is very debatable. If I move behind cover, that could certainly render me less able to effectively put my weapon between you and my body, or threaten you, etc. So it really depends on exactly what the narrative reason is for getting opportunity attacks in the first place (which is never spelled out).

Fourth, if anyone moves from 'no cover' to 'full cover' I would argue there is a state of '3/4 cover' inbetween, so attacks of opportunity against someone moving behind cover should come at a +5 AC.
(This neatly ties into my third point, because the 3/4 cover would also apply to the target threatening the character doing the opportunity attack.)

[Tes]

The issue here is that the rule is completely clear to me. It's why I keep hammering on about light switches and mugs in cubicles.
I simply can't fathom anybody seriously saying "Is there mug within your reach?" "Yes." "Can you grab it for me?" "No, there is a wall in the way."

Funny, from where I stand something I can not reach because of a wall would be clearly outside of my reach if queried in a casual conversation like this.

[Segev]

Funny, from where I stand something I can not reach because of a wall would be clearly outside of my reach if queried in a casual conversation like this.

That is the point the person you quoted was making.

[Zuras]

The official rules for how it works in 5e are pretty dumb in the edge cases. When I asked Sage Advice their answer was that moving where you can’t physically be attacked provokes an AoO, but moving somewhere within physical range out of sight does not.

That interpretation leads to nonsensical outcomes like a ghost phasing into a wall provoking an attack, but a ghost moving through the illusion of a wall not provoking an attack (and then moving away without being further attacked).

The 5e rules in this regard are playable, but bear no relation to reality upon further inspection. You can walk all the way around someone with less risk than backing five feet away from them, which is obviously ludicrous to anyone who has watched a fencing match or SCA event.

[Segev]

The official rules for how it works in 5e are pretty dumb in the edge cases. When I asked Sage Advice their answer was that moving where you can’t physically be attacked provokes an AoO, but moving somewhere within physical range out of sight does not.

That interpretation leads to nonsensical outcomes like a ghost phasing into a wall provoking an attack, but a ghost moving through the illusion of a wall not provoking an attack (and then moving away without being further attacked).

The 5e rules in this regard are playable, but bear no relation to reality upon further inspection. You can walk all the way around someone with less risk than backing five feet away from them, which is obviously ludicrous to anyone who has watched a fencing match or SCA event.

Personally, while I'd rule one way, I am fine with EITHER the rules always treating you as provoking OAs if you're moving to a position from which you could not be attacked, OR if it treated moving into a position with total cover or total concealment as not provoking OAs as long as no other reason exists why it would provoke.

Consistency is the important thing, here, in gameplay.

[Rukelnikov]

FWIW this scenario happened yesterday in Solasta, and the game treated moving to full cover still within 5 ft (a wall in between) as provoking, I still don't agree but I guess its reasonable to have different interpretations.

[Zuras]

Personally, while I'd rule one way, I am fine with EITHER the rules always treating you as provoking OAs if you're moving to a position from which you could not be attacked, OR if it treated moving into a position with total cover or total concealment as not provoking OAs as long as no other reason exists why it would provoke.

Consistency is the important thing, here, in gameplay.

The problem with concealment provoking AoOs is that some outcomes just feel absurd. If moving into an illusionary wall otherwise within your opponent’s reach provokes, then the attack happens purely based on the perception of the attacker—the moving creature might not even be aware of the illusion at all!

[Witty Username]

I figure since the whole point is back stepping leaving one open if they don't cover themselves, I would say phasing through a wall provokes an attack. This feels like a grid caused problem.

[PhoenixPhyre]

I can't say this is the rules-mandated reading (if such exists), but my default reading can basically be summed up as

IF (A was within the area against which B could hit with a melee attack) AND (A moves so that he leaves that area) AND (B can see A at that point in the motion)
THEN (A provokes an opportunity attack from B before he actually leaves the stated area).

This means
- Step from light into darkness and reach doesn't extend into darkness? OA
- Step around a hard corner and gain total cover? OA
- Step from light into darkness and reach DOES extend into darkness (reach weapon, for example)? no OA
- Phase into the floor/wall/etc? OA
- Step from darkness (assuming no bypass for that) out of reach? No OA.

This, to me, is fairly player-friendly while still treating everyone the same. No juking OAs by going through the walls or around them for anyone. But there are more incorporeal NPCs than ways PCs have to do the same. And more creatures whose extended reach can be exploited via Darkness/loss of sight than PCs with extended reach.

[Segev]

The problem with concealment provoking AoOs is that some outcomes just feel absurd. If moving into an illusionary wall otherwise within your opponent’s reach provokes, then the attack happens purely based on the perception of the attacker—the moving creature might not even be aware of the illusion at all!

I am inclined to agree with you, and would rule accordingly. However, as long as rulings are consistent within the same game, I am not going to be too upset. It actually is probably to PC advantage to have it ruled the other way, because then Sentinel will let you keep ghosts from escaping into the floor, which is almost always going to happen more often than a PC wants to escape into a fog bank or around a ticket booth's back wall.

[Reynaert]

The problem with concealment provoking AoOs is that some outcomes just feel absurd. If moving into an illusionary wall otherwise within your opponent’s reach provokes, then the attack happens purely based on the perception of the attacker—the moving creature might not even be aware of the illusion at all!

I still believe the biggest absurdities arise when there is a discrepancy between the two opponents on who can attack the other. Your scenario is another example of this.

So (as I already said somewhere at the beginning of this thread) if I were to house-rule this, it would get flipped. So if A moves, then B gets an opportunity attack just before B gets out of reach of A. Sure, it's a bit more difficult to express, but I think the idea is clear?

True, this gives a significant advantage to reach weapons, but I'd say that's an added benefit to this house rule ^^

[Aimeryan]

First of all, the common English usage is not ambiguous at all. Normally (in 5e), either a game term is defined as a game term, or its usage is common English.
The only reason ambiguity is being introduced is because the consequences feel "less natural" to some people. So this feels a lot like circular reasoning.

Second, the term reach is used in the description of total cover, saying that "some spells can reach such a target", implying that normally an attack or a spell can not "reach" such a target. So that is arguably the "mentioned at least once" you wanted.

Third, "using cover shouldn't make you more vulnerable" is very debatable. If I move behind cover, that could certainly render me less able to effectively put my weapon between you and my body, or threaten you, etc. So it really depends on exactly what the narrative reason is for getting opportunity attacks in the first place (which is never spelled out).

Fourth, if anyone moves from 'no cover' to 'full cover' I would argue there is a state of '3/4 cover' inbetween, so attacks of opportunity against someone moving behind cover should come at a +5 AC.
(This neatly ties into my third point, because the 3/4 cover would also apply to the target threatening the character doing the opportunity attack.)

1. No, it is ambiguous because we don't know if WotC meant the common English term or the term they appear to be using whenever melee attacks are considered. There is something to be said for using common English when there is no other choice, however, when there does appear to be some attempt at a definition it becomes ambiguous.

2. Good point, however, this is not referencing melee attacks but a Spell, which is not the same. You are correct that Spells do consider cover, as do ranged attacks in general. Consider the topic title is regarding threatened area. Now find one for melee attacks.

3. By extention, however, the same is true for the opponent. It isn't really an opportunity if something just became more difficult than before.

4. 5e does not have that granularity. Once again, though, it doesn't really make sense that you get an extra attack because something is just about to become impossible or more difficult. The opportunity attack is poorly worded if the goal is in actuality just a penalising attack anytime you think someone should be punished for doing something (consider that casting spells right next to someone with somatic components does not activate this).

Honestly, I don't think your wrong by ruling this way - I just think you have another option and that option is superior in narrative.

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On a slightly different note, I think without facing rules and with turn-based play trying to simulate the idea of attacking someone in the back as they move is just too problematic. When tried by D&D you have the 3.5e rules of provoking due to any movement within range, and the 5e rules of provoking due to any movement transitioning out of range. The first makes it too penalising to move at all once enjoined, the second makes for weird simulation where is it not provoking to move around #1 and attacking #2 which would definitely have your back to #1, but to just back off 5ft from #1 does provoke.

I wonder if a better rule would just be that moving while in the threatened area of an enemy acts as difficult terrain? It simulates acting as a soft barricade against opponents, while not being overly punishing to movement at all. It also avoids this weird interaction of knowing whether something is going to be out of reach or not (consider Zuras' illusionary wall example).