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. 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. If the target willingly moves before then, it immediately takes 1d8 thunder damage, and the spell ends.
Twinned Spell:
When you cast a spell that targets only one creature and doesn’t have a range of self, you can spend a number of sorcery points equal to the spell’s level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip).
Twinned spell allows you to select another target with a spell already cast. What it doesn't do is instantly have you cast the spell a second time. Since the melee weapon attack is "part of the action used to cast this spell", twinned spell would not let you make another melee weapon attack. By RAW, the effect on the target (on hit) is that the target "suffers the attack's normal effects, and (move and boom)". So I'd say by RAW twinning a booming blade that hits would double the melee attack damage as well as the thunder damage, but you wouldn't get to make another attack.
In terms of how the spell actually works, I envision a caster doing some magic hocus pocus for a few seconds to "prep" their weapon, and then making an attack with their magically charged weapon. Twinned spell would double the charge, so the weapon would just deal normal slashing/bludgeoning/piercing damage but if the target moves it will take 2d8 instead of 1d8 thunder damage.
I thought it was like an after Image of your attack is applied to a second target? Like mage hand is holding whatever weapon you are and strikes the second target as you strike the first. It's one attack. Two instances of the same damage.
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. 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. If the target willingly moves before then, it immediately takes 1d8 thunder damage, and the spell ends.
Twinned Spell:
When you cast a spell that targets only one creature and doesn’t have a range of self, you can spend a number of sorcery points equal to the spell’s level to target a second creature in range with the same spell (1 sorcery point if the spell is a cantrip).
Twinned spell allows you to select another target with a spell already cast. What it doesn't do is instantly have you cast the spell a second time. Since the melee weapon attack is "part of the action used to cast this spell", twinned spell would not let you make another melee weapon attack. By RAW, the effect on the target (on hit) is that the target "suffers the attack's normal effects, and (move and boom)". So I'd say by RAW twinning a booming blade that hits would double the melee attack damage as well as the thunder damage, but you wouldn't get to make another attack.
In terms of how the spell actually works, I envision a caster doing some magic hocus pocus for a few seconds to "prep" their weapon, and then making an attack with their magically charged weapon. Twinned spell would double the charge, so the weapon would just deal normal slashing/bludgeoning/piercing damage but if the target moves it will take 2d8 instead of 1d8 thunder damage.
I thought it was like an after Image of your attack is applied to a second target? Like mage hand is holding whatever weapon you are and strikes the second target as you strike the first. It's one attack. Two instances of the same damage.
It is not. In fact, the second instance of damage isn't attack damage.
I agree with you since it would be akin to the great weapon master (5e's version of cleave) or.even better, the ranger hunter archetype's ability horde breaker. You hit one enemy and keep swinging through to hit another enemy.
I thought it was like an after Image of your attack is applied to a second target? Like mage hand is holding whatever weapon you are and strikes the second target as you strike the first. It's one attack. Two instances of the same damage.
It is not. In fact, the second instance of damage isn't attack damage.
I agree with you since it would be akin to the great weapon master (5e's version of cleave) or.even better, the ranger hunter archetype's ability horde breaker. You hit one enemy and keep swinging through to hit another enemy.
Booming blade has a range of self with an area of 5ft so it cannot be twinned.