D&D 5E Using booming blade on a reaction attack with sanctuary question

[Stoutstien]

I’ve never seen a case where someone wanted to do that, but sure.

Not uncommon with doom booming. Even if they aren't under the BB effect before they decide to move getting tagged by a BB AO could change their plan.
Same for feints tactics to draw AOs to eat reactions so more detrimental ones can't occur. Popular for some BM fighters wanting to trigger a reaction maneuver without giving up ground.

 

[Maxperson]

Booming blade doesn’t target an enemy. It has a range of “self” and the effect of allowing you to make a melee weapon attack with the weapon used for the material component, which has a special effect if it hits.

Like I said, it’s ambiguous enough that I can see how someone might interpret it differently, and it’s not really relevant to the topic. But that’s my understanding of how Booming Blade works.

I would allow it. The intent of Warcaster is to A) enable you to cast a spell as a AOO reaction, and B) do so to hurt the enemy. While it technically doesn't target the enemy directly, it's fast enough and intended to hurt and I don't see why a caster wouldn't be able to do it.

 

[Maxperson]

Somewhat related to the question at hand: do you people allow someone who has been targeted by an OA triggered by leaving reach to interrupt their movement and decide to remain where they are?

No. Otherwise the trigger would never have occurred, leaving them no reason to stop short of leaving the area.

 

[Maxperson]

1 - enemy starts to move away
2 - AoO triggers and is taken before the enemy leaves their square. Sanctuary drops.
3 - Enemy can decide not to move:
3a - if they move they take damage from Booming Blade for moving, they only take this once because the 2 uses of it overlap and trigger at the same time.
3b - if they decide not to move they do not take the extra damage from Booming blade and is standing next to the PC. They can attack them if they like.

When Booming Blade is used on someone they can decide to stop moving to avoid the extra damage from moving.

Number 3 isn't an option. They have left the area already. The trigger happens as they are leaving, but the enemy has already gone that 5 feet. They can come back, but they cannot decide to stop.

 

[Maxperson]

The enemy doesn't have to move after being hit by an Opportunity Attack according to the Devs
So the sequence would go more as follow. Enemy is sheathed in booming energy to start his turn and right next to me.

Enemies Turn:
1. Enemy attempt moving out of my reach, triggering an AOO
2. Cast Booming Blade via War Caster, hitting it and sheathing it in booming energy
3. Sanctuary drops
4. The enemy either keep moving and take damage from Booming Blade or stay within 5 feet of me and attack me

Another insanely silly Crawford ruling. The enemy is in motion going 5 feet away. They get hit as they are leaving, but both momentum and the fact that if they stop without actually leaving reach, there could be no opportunity attack to make them want to stop moving mean that they need to go at least 5 feet away and then decide to stop or move somewhere else.

 

[Stoutstien]

No. Otherwise the trigger would never have occurred, leaving them no reason to stop short of leaving the area.

The trigger is "right before the creature leaves.."
Unless your AO includes a feature that forces the target to continue moving they can just stop... meaning they have spend the movement but remained I'm the same "space".
It's a result of the how the game breaks up space And movement into grids for playability.

**AOs are already silly. Moving away from a someone swinging a weapon almost always decreases the opportunities for them to hit you. Image if you gave a put two guys in a large room and gave one a stick and told the other one to not get touched by the stick. In what reality is moving towards the stick going to increase your odds of not to getting poked?

 

[Maxperson]

The trigger is "right before the creature leaves.."

The trigger can ONLY happen if the creature leaves reach. It THEN interrupts and happens before you leave, but if you never leave there was never a trigger in the first place. In effect, if you allow the creature to stop, you are allowing it to negate the AOO as it never left and never triggered that attack.

 

[ECMO3]

2 - AoO triggers and is taken before the enemy leaves their square. Sanctuary drops.

I don't think this is true. The AOO happens right before they leave my "reach". They have already moved before the AOO is triggered. With a 5 feet of movement they have moved almost entirely out of their sqaure they were in and are almost entirely inside the square they moved to. If you are going to put them inside one square or the other it would be the one they are going to. It would also take almost 10 movement to move back to the center of the square they were in (almost 5 to move out, almost 5 to move back). I can see the arguement that they are still within reach when it triggers and can attack me without moving more, but not the arguement that they are in their original square.

I also think he takes the original booming blade damage because the wording of the booming blade spell is "target willingly moves 5 feet or more". Moving 5 feet moves him to the extent of my reach. An enemy that is exactly 5 feet away is exactly at the edge of my reach (when the AOO happens) and the spell triggers at exactly that same range as well.

If the spell said "target willingly moves more than 5 feet" then he would not take the damage, but "5 feet or more" would mean he does I think.

 

[Maxperson]

I don't think this is true. The AOO happens right before they leave my "reach". They have already moved before the AOO is triggered. With a 5 foot move they have moved almost entirely out of their sqaure they were in and are almost entirely inside the square they moved to. If you are going to up them inside one square it would be the one they are going to. It would also take almost 10 movement to move back to the center of the square they were in (almost 5 to move out, almost 5 to move back)

I can see the arguement that they are still within reach, but not the arguement that they are in their original square.

I also think he takes the booming blade damage because the wording of the booming blade spell is "target willingly moves 5 feet or more". Moving 5 feet moves him to the extent of my reach. An enemy that is exactly 5 feet away is exactly at the edge of my reach, the spell triggers at the same time as the AOO triggers.

If the spell said "target willingly moves more than 5 feet" then he would not take the damage, but "5 feet or more" would mean he does.

They're relying on another silly Crawford ruling and not RAW.

 

[Stoutstien]

The trigger can ONLY happen if the creature leaves reach. It THEN interrupts and happens before you leave, but if you never leave there was never a trigger in the first place. In effect, if you allow the creature to stop, you are allowing it to negate the AOO as it never left and never triggered that attack.

If they leave then they are out of range so the AO can't happen. The only logical conclusion that works with all the other factors, like sentinel and BB , is the movement of space is attempted, the the reaction occurs, then the movement is resolved. That can only happen of the target has agency over where they are.

In other words they moved 4 ft and the AO happens. They then can continue to move or stay where they are. Nothing in the rules say you must spend movement in set chunks.