There's actually debate on whether Booming Blade can be used as an opportunity attack paired with Warcaster. The problem is that Tasha's errata's Booming Blade to target Self (since you're essentially casting the spell on your own weapon, then using it to attack), but Warcaster only allows spells that Target just the creature that triggered the opportunity attack.
Then there's also debate on whether the creature automatically triggers the booming effect, since it's the act of moving away that triggers the OA, or whether the creature can recognize that it's been hit, then choose to remain in place. Although I suppose it makes sense that a creature doesn't need to complete its movement to trigger on OA, otherwise Sentinel wouldn't be able to pin a target in place.
"Range" does not mean the same thing as "Target".
There is no "Target" field in spells and the target(s) are always specified in the spell's description. A range of self does not make you the target of the spell yourself much like the "Friends" spell has a range of self but targets one creature of your choice or Lightning Lure which has a range of "Self" yet let's you target a creature 15 feet away from you. The same is true for Booming blade, it has a range of self (5-foot radius) but targets ONE creature within 5 feet of you. There are tons of "Self" ranged spells that target other creatures: Burning Hands, Color Spray, Frost Fingers, Thunderwave, etc. These spells with a range of self usually just mean that they emanate from you and you can't choose another point of origin.
The errata in the case of the SCAGtrips here was really just a bad and confusing attempt at preventing the use of the "Twinned" metamagic which SPECIFIES that it must only target one creature and NOT have a range of self, thus, disqualifying these cantrips from using this metamagic option which was clearly broken anyway. That's really all there is to it.
Edit:
All spells with a "line of effect" and all "cone" spells whose point of origin is yourself all have a range of "Self". This is specified in page 202 of the PHB. The part about the target(s) being specified in the spell's description is also mentioned in the PHB on page 204. This means that Booming Blade's target is a creature (not yourself) and is thus legal to use with War Caster RAW and RAI. Anybody telling you otherwise is just wrong.
"Secondary" targets. These need not be in Range of the spell and can be behind total cover. These are generally anything that is affected by the spell's effects.
For example, Fireball can target a point in space A adjacent to a space B where B is behind total cover relative to the caster and is out of range, meaning anything in B can't be targeted for two reasons at once, provided A is within range and not behind total cover. Should the spell go off, the spell can then damage a creature in space B, and the damaged creature is also, by definition, targeted by the spell.
By your own link, Range is not the same as Target. It says that the Target must be within the range, and the range of Booming Blade is Self (5 feet). So a creature within 5 feet of you would absolutely qualify as being a target within range.
No, that's not what 5-foot radius means. I linked you to the rules. Booming Blade can no more pick a primary target within the spell's radius than Burning Hands or Fireball can - the spell's area is used to determine secondary targets, not primary targets (as I said, this is nomenclature I introduced - the RAW doesn't use those terms).
Booming Blade has the same rules as Burning Hands, except that its AOE is not a cone, it's a radius - e.g. the same AOE as Antimagic Field. Booming Blade targets the caster as the point of origin of an AOE (see above; AOEs are expected to sometimes have a creature as their point of origin), and then that AOE is a defined radius.
Booming Blade does have the same rules as Burning Hands, in that the spell has a specifically defined point of origin, this does not make that point of origin the target, the target is defined in the text of the spell, explicitly stating the effects of the spell on said target. Booming Blade is not an Area of Effect spell, but even if it where, the targets of an AoE spell are those affected within the area and not explicitly the point of origin, which may or may not be part of the target depending on the spell.
"Secondary" targets. These need not be in Range of the spell and can be behind total cover. These are generally anything that is affected by the spell's effects.
For example, Fireball can target a point in space A adjacent to a space B where B is behind total cover relative to the caster and is out of range, meaning anything in B can't be targeted for two reasons at once, provided A is within range and not behind total cover. Should the spell go off, the spell can then damage a creature in space B, and the damaged creature is also, by definition, targeted by the spell.
No, it doesn't, that part in the rules simply states that spells that DO only target you have a range of "Self". Not the opposite!
Nowhere does it say that ALL spells with a range of "Self" make the caster the target. That is simply your own misinterpretation of this sentence.
Also, there is no such thing as a "primary/secondary" target. You are either a target or you are not and the rules for targetting explicitly say that the TARGETS are specified in the spell's description and do not reference range anywhere. They also explicitly mention that spells have targets AND points of origin which are not the same. See here -> https://www.dndbeyond.com/sources/basic-rules/spellcasting#Targets
TL;DR: A range of "Self" means you are the spell's point of origin, if any, but do not necessarily mean that you are the spell's target. Valid targets are always specified in a spell's description.
That would literally mean the caster is the one taking the damage, which, I think we can all agree is a ridiculous interpretation.
On a hit, the target suffers the weapon attack’s normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target willingly moves 5 feet or more before then, the target takes 1d8 thunder damage, and the spell ends.
That would literally mean the caster is the one taking the damage, which, I think we can all agree is a ridiculous interpretation.
No it wouldn't. A spell does not have to do the same thing to all of its targets. All AOEs target their point of origin, but e.g. Fireball doesn't damage its point of origin.
On a hit, the target suffers the weapon attack’s normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target willingly moves 5 feet or more before then, the target takes 1d8 thunder damage, and the spell ends.
That's not what "the target" means in context - you chopped off the preceding sentence, so your quote is misleading. These two sentences refer to the melee attack's target, not the spell's "target" (and the spell has two targets, as I've said). Here's the full quote, and I'll add annotations in square brackets to make it clear.
You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target [of the attack] suffers the weapon attack’s normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target [of the attack] willingly moves 5 feet or more before then, the target [of the attack] takes 1d8 thunder damage, and the spell ends.
That would literally mean the caster is the one taking the damage, which, I think we can all agree is a ridiculous interpretation.
No it wouldn't. A spell does not have to do the same thing to all of its targets. All AOEs target their point of origin, but e.g. Fireball doesn't damage its point of origin.
On a hit, the target suffers the weapon attack’s normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target willingly moves 5 feet or more before then, the target takes 1d8 thunder damage, and the spell ends.
That's not what "the target" means in context - you chopped off the preceding sentence, so your quote is misleading. These two sentences refer to the melee attack's target, not the spell's "target" (and the spell has two targets, as I've said). Here's the full quote, and I'll add annotations in square brackets to make it clear.
You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a hit, the target [of the attack] suffers the weapon attack’s normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target [of the attack] willingly moves 5 feet or more before then, the target [of the attack] takes 1d8 thunder damage, and the spell ends.
Range of self can mean you are the target (like shield) or you are the point of origin. Booming Blade involves a melee attack as part of the Cast a Spell action, and you target a single creature with that attack, and only that target receives the effects of the spell.
This is no different than Cone of Cold, in which "self" means it originates from you.
Cone of Cold:
Range/Area
Self (60 ft )
Booming Blade:
Range/Area
Self (5 ft )
Are you also claiming the caster is the target of Cone of Cold?
I'm a little unsure on how to utilise this cantrip. On the surface, I thought the idea was that you hit them with it, retreat, and then the enemy has a choice of either pursuing you/attacking someone else and sucking up 1d8 thunder damage, or staying within 5ft of where it started its turn. It's a nice bonus to add to your attack - either extra damage or pinning your opponent to a place that they can't retaliate.
Then I realised that doing that would, in most cases, provoke an Attack of Opportunity, because you have to be within 5ft of them to start the cantrip, then for it to work I'd have to leave that 5ft range which happens to be the range of most attacks, creating an AoO for them, defying the point. Then really, I'm trading an AoO for the opportunity to deal 1d8 thunder...doesn't seem quite so great.
Is that the intent? Or is it just intended as a soft version of compelled duel - fight me, or take 1d8 thunder damage if you go for someone else? Or am I just missing something?
Yes this is the intent. And it’s great. Think of a blade pact warlock. They rely on those opportunity attacks to do a lot of their damage (via Armour of Agathis, hellish rebuke). Other hit and run combatants like a bladesinger use high armour class, song of defence or the shield spell to counter those opportunity attacks. (Rogues do the same thing with things like uncanny dodge, rangers and monks have stuff too). Those opportunity attacks are a tactical trade-off for battlefield control that you can either negate or use to your advantage.
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"Range" does not mean the same thing as "Target".
There is no "Target" field in spells and the target(s) are always specified in the spell's description. A range of self does not make you the target of the spell yourself much like the "Friends" spell has a range of self but targets one creature of your choice or Lightning Lure which has a range of "Self" yet let's you target a creature 15 feet away from you. The same is true for Booming blade, it has a range of self (5-foot radius) but targets ONE creature within 5 feet of you. There are tons of "Self" ranged spells that target other creatures: Burning Hands, Color Spray, Frost Fingers, Thunderwave, etc. These spells with a range of self usually just mean that they emanate from you and you can't choose another point of origin.
The errata in the case of the SCAGtrips here was really just a bad and confusing attempt at preventing the use of the "Twinned" metamagic which SPECIFIES that it must only target one creature and NOT have a range of self, thus, disqualifying these cantrips from using this metamagic option which was clearly broken anyway. That's really all there is to it.
Edit:
All spells with a "line of effect" and all "cone" spells whose point of origin is yourself all have a range of "Self". This is specified in page 202 of the PHB. The part about the target(s) being specified in the spell's description is also mentioned in the PHB on page 204. This means that Booming Blade's target is a creature (not yourself) and is thus legal to use with War Caster RAW and RAI. Anybody telling you otherwise is just wrong.
Yes it does.
Booming Blade, by definition, targets the caster, in the exact same way Burning Hands does.
Essentially, AOE spells in the general sense target in two steps:
For example, Fireball can target a point in space A adjacent to a space B where B is behind total cover relative to the caster and is out of range, meaning anything in B can't be targeted for two reasons at once, provided A is within range and not behind total cover. Should the spell go off, the spell can then damage a creature in space B, and the damaged creature is also, by definition, targeted by the spell.
No, that's not what 5-foot radius means. I linked you to the rules. Booming Blade can no more pick a primary target within the spell's radius than Burning Hands or Fireball can - the spell's area is used to determine secondary targets, not primary targets (as I said, this is nomenclature I introduced - the RAW doesn't use those terms).
Spells such as burning hands and cone of cold cover an area, allowing them to affect multiple creatures at once. A spell's description specifies its area of effect, which typically has one of five different shapes: cone, cube, cylinder, line, or sphere. Every area of effect has a point of origin, a location from which the spell's energy erupts. The rules for each shape specify how you position its point of origin. Typically, a point of origin is a point in space, but some spells have an area whose origin is a creature or an object. A spell's effect expands in straight lines from the point of origin. If no unblocked straight line extends from the point of origin to a location within the area of effect, that location isn't included in the spell's area. To block one of these imaginary lines, an obstruction must provide total cover.
Booming Blade has the same rules as Burning Hands, except that its AOE is not a cone, it's a radius - e.g. the same AOE as Antimagic Field. Booming Blade targets the caster as the point of origin of an AOE (see above; AOEs are expected to sometimes have a creature as their point of origin), and then that AOE is a defined radius.
Booming Blade does have the same rules as Burning Hands, in that the spell has a specifically defined point of origin, this does not make that point of origin the target, the target is defined in the text of the spell, explicitly stating the effects of the spell on said target. Booming Blade is not an Area of Effect spell, but even if it where, the targets of an AoE spell are those affected within the area and not explicitly the point of origin, which may or may not be part of the target depending on the spell.
No, it doesn't, that part in the rules simply states that spells that DO only target you have a range of "Self". Not the opposite!
Nowhere does it say that ALL spells with a range of "Self" make the caster the target. That is simply your own misinterpretation of this sentence.
Also, there is no such thing as a "primary/secondary" target. You are either a target or you are not and the rules for targetting explicitly say that the TARGETS are specified in the spell's description and do not reference range anywhere. They also explicitly mention that spells have targets AND points of origin which are not the same. See here -> https://www.dndbeyond.com/sources/basic-rules/spellcasting#Targets
TL;DR: A range of "Self" means you are the spell's point of origin, if any, but do not necessarily mean that you are the spell's target. Valid targets are always specified in a spell's description.
That would literally mean the caster is the one taking the damage, which, I think we can all agree is a ridiculous interpretation.
On a hit, the target suffers the weapon attack’s normal effects and then becomes sheathed in booming energy until the start of your next turn. If the target willingly moves 5 feet or more before then, the target takes 1d8 thunder damage, and the spell ends.
No it wouldn't. A spell does not have to do the same thing to all of its targets. All AOEs target their point of origin, but e.g. Fireball doesn't damage its point of origin.
That's not what "the target" means in context - you chopped off the preceding sentence, so your quote is misleading. These two sentences refer to the melee attack's target, not the spell's "target" (and the spell has two targets, as I've said). Here's the full quote, and I'll add annotations in square brackets to make it clear.
Range of self can mean you are the target (like shield) or you are the point of origin. Booming Blade involves a melee attack as part of the Cast a Spell action, and you target a single creature with that attack, and only that target receives the effects of the spell.
This is no different than Cone of Cold, in which "self" means it originates from you.
Cone of Cold:
Also,
https://twitter.com/OregonRolledA20/status/1326595828371222528?ref_src=twsrc^tfw|twcamp^tweetembed|twterm^1326596181560942593|twgr^|twcon^s2_&ref_url=https://www.redditmedia.com/mediaembed/jse10i?responsive=trueis_nightmode=false
Yes this is the intent. And it’s great. Think of a blade pact warlock. They rely on those opportunity attacks to do a lot of their damage (via Armour of Agathis, hellish rebuke). Other hit and run combatants like a bladesinger use high armour class, song of defence or the shield spell to counter those opportunity attacks. (Rogues do the same thing with things like uncanny dodge, rangers and monks have stuff too). Those opportunity attacks are a tactical trade-off for battlefield control that you can either negate or use to your advantage.
Check out my Disabled & Dragons Youtube Channel for 5e Monster and Player Tactics. Helping the Disabled Community and Players and DM’s (both new and experienced) get into D&D. Plus there is a talking Dragon named Quill.
https://www.youtube.com/channel/UCPPmyTI0tZ6nM-bzY0IG3ww