D&D 5E Point me to the rule please:

[FormerlyHemlock]

Can't really ask that when you cut the part that answers the question. You know, the whole part about how no world is perfect and time is focused on priorities which include things the players will encounter, and the analogy to the worm, etc..you know, most of the post which was devoted to answering that question?



Why do you get an opportunity attack only for a hostile creature leaving your threatened area (that's the rule, in black and white, no question about it), and not for an ally leaving that area? All of a sudden you seem focused on balance issues (1/4 vs 1 action), which you earlier claimed was not your concern...

That's not a balance issue.

Except for rules lawyering, there's no reason you could not opportunity attack a friendly creature, e.g. to keep a barbarian enraged, or to commit betrayal. The rule says "hostile" because that's the common case. I don't think the word is a significant crunch restriction.

I'm done in this thread unless new voices speak up with new questions.

 

[Mistwell]

That's not a balance issue.

How is it not a balance issue? What meaning does 1/4 vs 1 have, if it's not about relative power of the ability? You were talking in-world justifications. In-world justifications are just as important whether it's 1/4 an action, or a full action, right? In fact, you said as much earlier. It's only power/balance that is a difference there. It's the issue you raised, why don't you explain?

Except for rules lawyering, there's no reason you could not opportunity attack a friendly creature

It's not rules lawyering. There's nothing hazy about the rule, you're not interpreting the rule in some favorable manner or something, the rule is utterly clear and nobody has ever expressed any doubts about it. That's not rules lawyering, it's just a rule. The rule is you only get an opportunity attack if it's a hostile creature leaving your threatened space, not for an ally.

And yes, if it could apply to allies, it would sometimes be beneficial, particularly when combined with some charm type spells on monsters who would not only be attacking an ally for that round (per the spell) but might then be attacking their allies (though the spell doesn't specify that), and I think it might have some issues with some feats as well, grappling an ally when they leave your threatened space because you're preventing them from heading into a trap you know about and they do not, etc... Again, the focus of this isn't "who can I attack with an opportunity attack", it's "when is an opportunity attack triggered". They don't trigger for allies leaving your threatened area. What is your in-world explanation for why that is, and what will you say when your players ask about it?

The rule says "hostile" because that's the common case. I don't think the word is a significant crunch restriction.

No it says hostile because that's the rule, it's EVERYWHERE in the rules (I quoted a half dozen, I could easily quote a dozen), and it's intentional and related to what the designers encountered in some prior editions where they didn't carve out that design space and some things functioned wonky because of it. In fact, why don't you ask Crawford or Mearls about it - I feel quite sure they will confirm it was intentional and not just a "common" case but because they don't want those things functioning against allies for a variety of reasons. Crunch reasons. Balance reasons. Flavor reasons. Many reasons.

I'm done in this thread unless new voices speak up with new questions.

OK, that's cool. For what it is worth, if you decide later to come back, I still genuinely do want to know why opportunity attacks only trigger when a hostile creature leaves your threatened space in your game, OR why 1/4 action vs 1 action is relevant if it's not an issue of balance. These seem like questions that help inform your decision on the feat in question.

 

[FormerlyHemlock]

And yes, if it could apply to allies, it would sometimes be beneficial, particularly when combined with some charm type spells on monsters who would not only be attacking an ally for that round (per the spell) but might then be attacking their allies (though the spell doesn't specify that), and I think it might have some issues with some feats as well, grappling an ally when they leave your threatened space because you're preventing them from heading into a trap you know about and they do not, etc... Again, the focus of this isn't "who can I attack with an opportunity attack", it's "when is an opportunity attack triggered". They don't trigger for allies leaving your threatened area. What is your in-world explanation for why that is, and what will you say when your players ask about it?

As explained previously, I'll go for consistency and rule that there is no targetting restriction.

"Sure, you can attack an ally if you really want to. But you can't grapple on an opportunity attack--PHB says you can only grapple on your turn with a regular attack."

 

[Mistwell]

As explained previously, I'll go for consistency and rule that there is no targetting restriction.

So you'd houserule opportunity attacks now too? All to deal with this theoretical possibility of a player wanting to misuse an optional feat in an unusual way? Wow, that's a lot of juggling behind the scenes to adjust the rules to fit an unlikely scenario. I still think it would be a heck of a lot easier to simply come up with an explanation for why some things only work against hostiles. A LOT of spells specify it too, and monster abilities. Are you going to houserule all them as well?

"Sure, you can attack an ally if you really want to. But you can't grapple on an opportunity attack--PHB says you can only grapple on your turn with a regular attack."

Right, which is why I said certain feats and abilities.

Here, maybe this explanation might work better than all these houserules, and still maintain verisimilitude within your game world:

"A lot happens in 6 seconds of battle, and the hit or misses rolled are simply representative summaries of the entirety of the action going on sometimes, the feints and glancing blows and blocks and dodges and other maneuvers. When something is triggered due to the actions of something hostile to you, it's because it represents something about the nature of the clash happening in those six seconds which is unique to fighting a foe - an opening in the sparing, a moment of direct targeting with a spell, a lapse in defense due to a misstep, etc.. These are things that only involve a battle with a foe. Even if it's a reaction to a foe's movement, it's really just a last stab or attack in that 6 second series of back and forth attacks, sort of a tail-end of that series of clashes. This is something you've learned over time in battles with foes - you've studied it, it's become instinctual for you, you're operating on muscle memory to react to an opening in a foe's defenses. Those sorts of things don't happen with allies - you have not focused your battle instincts to react that way, your eyes are usually not focused on allies and their movements, your body position is usually foe-directed for defense, and all your general experience is focused on facing and fighting enemies while in battle. So even in the rare instance where you might want to react to an ally with something that specifies hostile, your honed battle skills just don't react in time because you have not gained the muscle memory and instincts to attack your allies like that. These elements of the game which specify "hostile" are themed on those openings and back-and-forth battle and instincts which are particular to fighting foes."

There, that should cover 90%+ of the instances where anyone would care about using it on an ally (and an Athletics or Acrobatics check might help with the other 10%). You no longer need literally a dozen or more houserules (because that's how many times "hostile" comes up as a keyword in this game, and that's just in the player's handbook and not even looking at all the monsters with abilities that trigger off hostiles, and probably magic items too in the DMG). I am betting your players, who you said previously are pretty reasonable, will be fine with that explanation.

 

[FormerlyHemlock]

So you'd houserule opportunity attacks now too? All to deal with this theoretical possibility of a player wanting to misuse an optional feat in an unusual way?

Yes to the first. No to the second. It's not because of Warcaster, it's because it makes more sense.

I don't buy your explanation (you can't ignore allies' body posture and movements and still fight cooperatively), but that's okay because I don't need it either. Please stop trying to persuade me to play like you. It ain't happening.

 

[Mistwell]

Yes to the first. No to the second. It's not because of Warcaster, it's because it makes more sense.

I don't buy your explanation (you can't ignore allies' body posture and movements and still fight cooperatively), but that's okay because I don't need it either. Please stop trying to persuade me to play like you. It ain't happening.

First, I didn't say you ignore your allies posture and movements, I said you're not trained to strike at them when they leave their defenses open in the same way you are trained and experienced and instinctively know how to strike when an enemy does that. And that was just one small part of a long explanation I provided.

Second, I am not trying to persuade you to "play like me". This isn't about play style (you never even asked about my playstyle so you wouldn't know how I play anyway). I was trying to help out and come up with an explanation that you'd be satisfied with that would result in you not having to houserule every rule, every monster, every item, just so many things, that specify the word "hostile". But hey, it's your game, if you'd prefer to make all those houserules instead, OK then. But please don't mistake this as some play style issue.

 

[Hriston]

But there is. And, it's the same language Warcaster uses. "You can make an opportunity attack when a hostile creature that you can see moves out of your reach." And this is not the only time this language comes up in the rules. In fact differentiating abilities based on whether or not there is a hostile or a hostile does something is entrenched across the rules.*



*Rage: "It ends early if you are knocked unconscious or if your turn ends and you haven’t attacked a hostile creature since your last turn or taken damage since then."
*Totem Warrior, Wolf: While you're raging, your friends have advantage on melee attack rolls against any creature within 5 feet of you that is hostile to you.
*Bear Warrior: While you’re raging, any creature within 5 feet of you that’s hostile to you has disadvantage on attack rolls against targets other than you or another character with this feature.
*Dark One's Blessing: Starting at 1st level, when you reduce a hostile creature to 0 hit points, you gain temporary hit points...
*Targeting yourself: If a spell targets a creature of your choice, you can choose yourself, unless the creature must be hostile or specifically a creature other than you.
*I am skipping more references, including a ton of spells that only specify things for hostile creatures.

To add to the list, here's something that I think bears directly on the issue of opportunity attacks:

Moving Around Other Creatures
You can move through a nonhostile creature’s space. In contrast, you can move through a hostile creature’s space only if the creature is at least two sizes larger or smaller than you.... If you leave a hostile creature’s reach during your move, you provoke an opportunity attack, as explained later in the chapter.

It may also be of interest to note actions that are conditioned on the target being considered a "foe", a term that is used interchangeably with the word "hostile".

Ranged Attacks
When you make a ranged attack, you fire a bow or a crossbow, hurl a handaxe, or otherwise send projectiles to strike a foe at a distance.

Melee Attacks
Used in hand-to-hand combat, a melee attack allows you to attack a foe within your reach.

So, apparently, RAW, you can't make a ranged or a melee attack against your ally, period, unless you can make the convoluted argument that your ally is actually your foe. It shouldn't be surprising that the same applies to opportunity attacks.

Opportunity Attacks
In a fight, everyone is constantly watching for enemies to drop their guard. You can rarely move heedlessly past your foes without putting yourself in danger; doing so provokes an opportunity attack.

You can make an opportunity attack when a hostile creature that you can see moves out of your reach.

We can see here how the terms "enemies", "foes", and "hostile creatures" are used interchangeably.

Also, apparently, you can't use the Help action to assist a hostile creature to make an attack.

Alternatively, you can aid a friendly creature in attacking a creature within 5 feet of you.

Interestingly, however, and maybe more to the point of the OP, the text of Polearm Master does not specify a hostile creature, but rather allows you to make an opportunity attack against any other creature that enters your reach.

 

[Hriston]

I went back and read the OP. This thread got pretty off track didn't it? To address the original question, I believe that Mearls and Crawford's rulings stem from the clause about having to be wielding a polearm at the time the opportunity attack is made. If you are, then I can't see how you could be attacking with a spell or any other weapon.

 

[FormerlyHemlock]

It may also be of interest to note actions that are conditioned on the target being considered a "foe", a term that is used interchangeably with the word "hostile".

So, apparently, RAW, you can't make a ranged or a melee attack against your ally, period, unless you can make the convoluted argument that your ally is actually your foe. It shouldn't be surprising that the same applies to opportunity attacks.

Excellent point, Hriston. That's a good illustration of why I don't view "hostile" as a significant crunch restriction. It doesn't take "dozens of house rules" to say, "Treat 'hostile' in PHB text as a usage guideline, not a restriction. E.g. you shouldn't attack friendly creatures with melee weapons but you're allowed to, and in some instances (e.g. Domination) it might even be a good idea." At most that's a single house rule.

It would be silly for me to insist otherwise.

 

[Hriston]

Excellent point, Hriston. That's a good illustration of why I don't view "hostile" as a significant crunch restriction. It doesn't take "dozens of house rules" to say, "Treat 'hostile' in PHB text as a usage guideline, not a restriction. E.g. you shouldn't attack friendly creatures with melee weapons but you're allowed to, and in some instances (e.g. Domination) it might even be a good idea." At most that's a single house rule.

It would be silly for me to insist otherwise.

I don't think a distinction between crunch and fluff is particularly helpful as there is no clear line of demarcation in this "rules as guidelines" edition. The way I like to look at it is that the terms hostile and friendly used here are the same designations defined in the DMG under Starting Attitude.

Two things are apparent from the DMG. First, it is up to the DM to determine what a creature's Starting Attitude is, so a player can't really change their character's attitude from friendly to hostile by simple declaration. Attitude in a character is revealed through actions. A hostile creature seeks to hinder the PC's goals, so if a character attempts to thwart another character's action, or is actually attempting to harm the other character, then that character should be considered hostile by the DM. The same is true if the character is trying to help another character. That character is friendly. Where this might be confusing is that the game is written with the assumption that adventuring parties are comprised of characters that are friendly to each other. This makes sense because the party is assumed to share a common goal that they are helping each other to achieve. However, this is not necessarily a static condition.

That's because the second thing to take away about attitudes is that they can change throughout an encounter, sometimes temporarily. The game assumes that everyone on one side of a conflict is friendly with each other, and that they are hostile to the other side. But what happens when a character chooses to attack a fellow party member? The character's stated goal is to harm the other character, so the character is hostile by definition. The character being attacked now seeks to prevent the first character from achieving that goal, so it is now likewise hostile simply because the assumption is that a character will defend itself. This shift in attitude occurs before the blow actually lands, so the attack is possible.

If, by contrast, the character's intent was to aid the other party member by buffing with a spell, then they obviously remain friendly to one another, and such an action could neither be considered an attack nor an opportunity attack.

So, I think you're correct in not viewing this type of language as restrictive. But I think its more helpful when interpreting the rules to view these instances as defining certain actions as typical of a hostile creature, rather than to simply disregard the language as "not crunch".