D&D 5E Can you twin booming blade

[Salthorae]

As a game, what if I wrote a Booming Blade that obviously did work in the other way?

If you're going to re-write the spell in that way I'd model it on shield. So:

Casting time: 1 reaction*
...
* - which you take when you hit with a melee weapon attack

That simplifies it so it's not something fully custom.

 

[Esker]

As a game, what if I wrote a Booming Blade that obviously did work in the other way?

Thundering Blade
Evocation


Level: Cantrip
Casting time: Special
Range: 5 feet
Components: V, M (a weapon)
Duration: 1 round


In order to cast this spell you must have done the Attack Action without using Extra Attack and hit a single creature within range of this spell. That creature becomes the target. The target is sheathed in booming energy until the start of your next turn. If the target willingly moves before then, it immediately takes 1d8 thunder damage, and the spell ends.
This spell's damage increases when you reach higher levels.

At higher level: At 5th level, the spell deals 1d8 thunder damage to the target when cast, and the damage the target takes for moving increases to 2d8. Both damage rolls increase by 1d8 at 11th level and 17th level.

Seems messy; you'd be introducing a whole new casting time ("special"). I think if you wanted a spell that was functionally almost equivalent to BB but not twinnable, you could just give it a range of self (radius of 5'), and say that when the spell is cast (rather than "as part of casting this spell"), you can immediately make one melee attack with a weapon (no action required). A creature in the spell's area who is hit by this attack is sheathed... etc. etc. as the spell's energy coalesces around them, etc. etc.

I guess this would technically alter how it interacts with spell sniper or distant spell for reach weapons too, but otherwise I think it's equivalent.

 

[Esker]

If you're going to re-write the spell in that way I'd model it on shield. So:

Casting time: 1 reaction*
...
* - which you take when you hit with a melee weapon attack

That simplifies it so it's not something fully custom.

This would potentially make it much more powerful, by allowing you to use it with multiple attacks, and pick an attack that hits. The extra cost is your reaction, and never being able to use it on AoOs or readied actions even with war caster, but I think you'd see a lot more martials picking this up if you changed it like this. (You've also made it work with unarmed strikes, taking it from a terrible option to an amazing one for monks)

 

[Salthorae]

This would potentially make it much more powerful, by allowing you to use it with multiple attacks, and pick an attack that hits. The extra cost is your reaction, and never being able to use it on AoOs or readied actions even with war caster, but I think you'd see a lot more martials picking this up if you changed it like this. (You've also made it work with unarmed strikes, taking it from a terrible option to an amazing one for monks)

How could you use it with multiple attacks? Do you mean as part of the Extra Attack? Yeah, I suppose, but it does use your reaction so there are not zero costs.

I didn't change the "M" component in my potential update to the custom update. So it still requires a melee weapon as the Material component, but a monk could use it as much as they always could with Monk weapons.

There was never anything stopping a Monk who had the cantrip from some source using it with their monk weapons (that use their martial arts die) and still using their bonus action for Flurry or their normal Bonus Action attack.

 

[NotAYakk]

If you're going to re-write the spell in that way I'd model it on shield. So:

Casting time: 1 reaction*
...
* - which you take when you hit with a melee weapon attack

That simplifies it so it's not something fully custom.

Sure, but I wanted to write the spell that matches what many people think Booming Blade does.

It doesn't quite match exactly, because quicken spell doesn't work on it, neither does warcaster. But still.

 

[Esker]

How could you use it with multiple attacks? Do you mean as part of the Extra Attack? Yeah, I suppose, but it does use your reaction so there are not zero costs.

One of the main things that balances the blade cantrips is that you can't use extra attack if you use them, since they require the 'cast a spell' action.

It's true that by making the casting time one reaction you're imposing a cost in addition to the benefit of being able to stack it with extra attack, but the effect of this is to make the cantrip worse for characters that would previously have used it instead of extra attack (also for characters who use bonus action spells, since this is no longer a 'cantrip with a casting time of one action' and thus can't be used on the same turn), and better for characters that would not have cared about having it because extra attack is better for them.

I didn't change the "M" component in my potential update to the custom update. So it still requires a melee weapon as the Material component, but a monk could use it as much as they always could with Monk weapons.

Yes, but a monk can be holding a staff in one hand and make unarmed strikes with the other. Having a weapon be a material component doesn't mean you have to use that weapon on the attack.

There was never anything stopping a Monk who had the cantrip from some source using it with their monk weapons (that use their martial arts die) and still using their bonus action for Flurry or their normal Bonus Action attack.

There was: both Flurry of Blows and the Martial Arts bonus attack require the attack action, which booming blade does not involve. So a monk could technically use it with their monk weapons, but it would be nearly pointless since (a) they'd have to give up their second attack, and (b) they'd have to give up their bonus action attack(s).

On top of that, monks don't have all that much that uses their reaction.

So if you change the casting time to 1 reaction, which you take when you hit with a melee weapon, a monk is virtually guaranteed to get the bonus damage most turns, since they're often making 4 attacks and are very unlikely to miss all 4. That makes the value of the cantrip very nearly a full 4.5 (assuming Tier 2); whereas as it is written, the value is 4.5 times your to-hit chance, and even then only if you wouldn't have made more than one attack.

 

[lumenbeing]

Magic?

That’s a pretty weak answer. “Magic” can only suspend disbelief so far. There is nothing in the spell description that says it gives the caster faster arms. Making the successful weapon attack is a REQUIREMENT of the spell, not an effect of the spell. That’s what the word “must” does here. it creates an special requirement.
Another implicit requirement of the spell is that there be a target. If there is only one target, Twinned Spell doesn’t “magically“ conjure another one for you to attack. Likewise it doesn’t magically endow the caster with an ability (eg. Second attack) she doesn’t already have.
Twinning BB should only be possible if the caster has an offhand weapon with which he could make a second weapon attack or otherwise has an ability granting him two attacks with the same weapon. If you are twinning the WHOLE SPELL as so many of you are vehemently arguing should be the case, then you are also twinning the requirement to make a successful weapon attack. And then, the whole spell should fail if EITHER attack misses.
The big fans of this exploit are happy to ignore common sense and logic. They are happy to imagine that requirements can simultaneously be effects and the paradox inherent therein. They are willing to imagine ghost arms and any other thing not actually written, while ignoring the word “must” that is actually part of the spell description. The logic these exploiters are proposing is this: “Twinned spell has a given list of requirements. If those are met, any other requirements imposed by the specific spell can be ignored”
Now a word on Jeremy Crawford’s tweets. JC was not the lead designer of SCAG, nor was he the lead editor. Very unlikely that he personally wrote Booming Blade. I don’t grant him the authority to retcon the RAI in this case. Whomever wrote the spell employed some creative writing to make an exceptional spell that works a a little differently from the normal spell casting mechanics. They didn’t think it all the way through in regards to twinned spell. The editors didn’t either. But JC would have us believe that everything they do is infallible and deliberate. His tweets are, as often as not, cryptic non answers, until he realizes he has painted himself in a corner and must finally give a yes or no.
Skeptics: “I smell a fart”
JC: “Nope. No one farted. There was no collusion”
Exploit fans: ”Well thank God that’s settled!”

 

[Esker]

That’s a pretty weak answer. “Magic” can only suspend disbelief so far. There is nothing in the spell description that says it gives the caster faster arms. Making the successful weapon attack is a REQUIREMENT of the spell, not an effect of the spell.

Most spells have requirements you have to perform to cast the spell. Twinning lets you double the ratio of effect to effort. Maybe in this case it does that by halving the effort required to make the attack. "Magic" is as good a justification as anything else when you're talking about what fluff to layer over a rule in a game that involves casting magic spells.

 

[Esker]

Another implicit requirement of the spell is that there be a target. If there is only one target, Twinned Spell doesn’t “magically“ conjure another one for you to attack.

What does that have to do with anything? Nobody is suggesting that twinning booming blade would let you attack a target that doesn't exist. You need two targets in range for it to work, just as you would if you were twinning, say, Shocking Grasp or Inflict Wounds.

Likewise it doesn’t magically endow the caster with an ability (eg. Second attack) she doesn’t already have. Twinning BB should only be possible if the caster has an offhand weapon with which he could make a second weapon attack or otherwise has an ability granting him two attacks with the same weapon.

The rules only specify the number of attacks you can make when you take the attack action. The attack you make as part of casting booming blade isn't part of the attack action, so there are no rules about how many times a sorcerer can make that kind of attack in a round.

If you are twinning the WHOLE SPELL as so many of you are vehemently arguing should be the case, then you are also twinning the requirement to make a successful weapon attack. And then, the whole spell should fail if EITHER attack misses.

There's no requirement to make a successful weapon attack. Just to make a weapon attack. It doesn't cause the spell to fail if the attack misses, although normally it just won't do anything anyway. If you twin it, though, you could well end up hitting one creature but not the other.

The big fans of this exploit are happy to ignore common sense and logic.

I'm not seeing how this is an exploit... In Tier 2, for 1 SP and an action you are doing something like, say, 4d8+6 or something damage (average 25) if you hit both targets (with a non-casting stat! Maybe more if the target moves or you've got some sort of STR-based multiclassed sorcerer with a bigger weapon). A Divine Soul sorcerer can twin Inflict Wounds for the same SP cost, getting 6d10 damage if they hit (average 33), using a CHA-based attack. Granted, that also uses a spell slot, but most sorcerers will run out of SP before they run out of spell slots, so it makes sense to use them when you will get the most bang for the buck out of them: the only way in which twining booming blade is better than twinning Inflict Wounds is that it lets you spread your resources out more, at the cost of getting a bit less out of them.

Well, and i guess the fact that you can quicken one thing and twin booming blade, which you can't do with Inflict Wounds. So if you want a more direct comparison, twinning toll the dead lets you do 4d12 damage (average 26), and at range.

Explain to me why being able to twin booming blade is an "exploit"?

 

[nogray]

Here's a purely-devil's-advocate alternate reading of the effect of twin-spelling a booming blade:

"As part of the action used to cast this spell, you must make a melee attack with a weapon against one creature within the spell’s range, otherwise the spell fails."

Okay; so we attack one creature with our melee weapon when we cast this spell. It is not directly stated that the creature we attack with our melee weapon needs to be the target of the spell, but I presume this is implied. If, for whatever reason, we can't take the attack, then the spell fails. If we can and we miss, the target (of the spell) suffers no effect. However, ...

"On a hit, the target suffers the attack’s normal effects, and it becomes sheathed in booming energy until the start of your next turn."

This seems to outline the effect of the spell on the target. The result of the spell is to cause the target (of the spell) to "suffer the attack's normal effect, and ...."

When you use twin spell, you get to "target a second creature in range with the same spell."

Putting that together, the ideal-nit-picky-rules-legal procedure seems to be as follows:

Cast the twin spell, simultaneously attacking one creature with your sword (or whatever). If the attack hits, the two targets (of the spell) will "suffer the attack's normal effect," (which includes the weapon damage and, at higher levels, the bonus d8s of thunder damage), and both targets (of the spell) will become "sheathed in booming energy until the start of your next turn."

This reading clearly separates the cost of "make a melee attack" from the effect of "suffer the attack's normal effect and [stuff with thunder and whatnot]."

I think it addresses the gold coin counterexample that @lumenbeing brought up. Imagine that the effect of the hypothetical "toss a gold coin" spell (let's call it ... "Leprechaun's Luck") is that the target gains a luck point (as the Lucky feat). Twinning this hypothetical spell would still only involve tossing one gold coin to one creature (similar to the one attack roll of Booming Blade), but two people would gain the luck point (similar to the weapon and thunder damage/effect of Booming Blade).

It also addresses @TheKing in not giving another attack roll. Indeed, only one attack roll is used. The other target just unluckily suffers an effect of a spell.

As I mentioned, this is a purely-devil's-advocate reading. How I would play or DM it would be in the "natural" reading of twinned spell --> two melee attacks, resolved individually (like @Esker and others mentioned).