D&D 5E Reacting to Movement

[W'rkncacnter]

How does that interact with Sentinel then?

i don't think comparing it to sentinel is fair because sentinel is effectively an interrupt. the enemy isn't deciding to do anything, YOU are locking THEM in place.

 

[James Gasik]

Right, well as I said, opportunity attacks can make their trigger impossible, but I don't think the provoking creature can choose not to initiate the trigger in the first place.

 

[Horwath]

To me explanation for AoO for moving away is simple.

Target turns it back towards you, then you make the attack.

Disengage is movement with your guard raised, ready to parry. so there in no AoO.

 

[Bacon Bits]

That's an odd ruling, isn't it though? I mean, the OA was triggered by the movement, it just resolves before the movement. By allowing the target to not move, then the trigger never happens in the first place? I'm pretty sure an OA can invalidate the trigger, but I don't think the target should be able to choose not to perform the trigger.

It's no more odd than using an OA to hit with an attack that reduces speed to 0 (e.g., a ghoul's claws).

Sometimes it makes sense to favor "reality" but often it is just much easier to let the game's abstraction of combat just do it's thing. Reactions break cause and effect in many cases. Most or all cases for some triggers. You either ignore that fact, or you probably need to rebuild the entire reaction actions section of the game from the ground up.

Right, well as I said, opportunity attacks can make their trigger impossible, but I don't think the provoking creature can choose not to initiate the trigger in the first place.

So if a character's movement causes them to step on a pressure plate that opens a pit 5 feet in front of them, you'd force them to fall into the pit?

 

[Sorcerers Apprentice]

The opportunity attack triggers when the enemy has moved 4.99999999.... feet. He then gets hit by booming blade, and decides to stop moving after moving an additonal 0.00000000000000...1 feet, which in this case is enough to put him out of range of the attacking character, but not enough to trigger the booming blade secondary effect.

 

[UngainlyTitan]

The opportunity attack triggers when the enemy has moved 4.99999999.... feet. He then gets hit by booming blade, and decides to stop moving after moving an additonal 0.00000000000000...1 feet, which in this case is enough to put him out of range of the attacking character, but not enough to trigger the booming blade secondary effect.

Yup, I would go along with that.

 

[NotAYakk]

Treat squares and 5' steps as an abstraction.

They leaving your reach. They are now boomed. They can stop moving right away in response in continuous movement case, like after 1 foot.

Mapping back to 5' squares, this means they don't actually leave the square, as 1 foot isn't enough. While they left reach, it is by not enough to matter.

 

[Seramus]

I rule it as "You are now standing 10' away, and under the effects of Booming Blade. Any ADDITIONAL movement will trigger it."

 

[Dausuul]

Hm, reading the text though, it says:

You can make an opportunity Attack when a Hostile creature that you can see moves out of your reach. To make the opportunity Attack, you use your Reaction to make one melee Attack against the provoking creature. The Attack occurs right before the creature leaves your reach.

This implies that the target has to leave your reach to trigger the attack, at which point, they can't just not leave your reach, or they wouldn't have triggered an opportunity attack in the first place.

But they also can't have actually left your reach yet, or you wouldn't be able to attack them. And you might reduce the target to 0 hit points or have the Sentinel feat, in which case it would never leave your reach at all.

And trying to "force through" the movement after the OA opens a can of worms. What if you used War Caster to cast vortex warp, teleporting the creature somewhere else? Does it have to move from its new location, and if so, which way? What if you put earthbind on it when it was trying to use flying movement, does it now have to walk? It's a lot simpler all around to let the target of an OA reconsider its decision to move after being attacked.

(Not that any of this matters for booming blade, since that effect only fires when the target moves more than 5 feet from where you hit it. Even if it does have to "finish" the provoking movement, it can get 1 inch beyond your reach and stop.)

 

[James Gasik]

It's no more odd than using an OA to hit with an attack that reduces speed to 0 (e.g., a ghoul's claws).

Sometimes it makes sense to favor "reality" but often it is just much easier to let the game's abstraction of combat just do it's thing. Reactions break cause and effect in many cases. Most or all cases for some triggers. You either ignore that fact, or you probably need to rebuild the entire reaction actions section of the game from the ground up.



So if a character's movement causes them to step on a pressure plate that opens a pit 5 feet in front of them, you'd force them to fall into the pit?

No, because that's not what's happening. The pressure plate activates when you step on it in this example.

Since you only provoke an opportunity attack after you leave someone's reach, a more appropriate analogy would be that there is a section of floor covering a pit that normally has some kind of locking mechanism to keep people from falling through. If you hit the pressure sensor, however, that lock is disengaged, and so, after leaving the section of floor it is located on, and then stepping on the now unlocked floor panel, stepping on it causes it to swing open and you fall.

Of course, in D&D, such a trap would probably allow for a Dexterity save, so an even more appropriate analogy would be, that, instead of a pit trap, there's a glyph of warding that explodes when you step on it. Either way, you can't look at it as "oh, I was moving, and that guy's sword is in front of me, I better stop".

You committed to moving, knowing you would provoke an opportunity attack from a foe whose space you are leaving. And then you got hit by it. Any rider effect attached to that attack that could prevent your movement certainly has it's normal effect, but you are still committed to leaving the attacker's reach. If you hadn't done so, or intended to do so (in the case of movement prevention), there wouldn't have been an opportunity attack in the first place.

And for all the "I only move a fraction of 5 feet" statements, if you're not 5' away, you haven't left the attackers reach.