This is very related to this question: Artificer Armorer Guardian attack and cantrips like Booming blade
This is to talk about the new rules introduced in TCoE with respect to Booming Blade and Green Flame Blade now needing "a melee weapon worth at least 1 sp" as the material cost (whereas before TCoE I believe it only needed a melee weapon)
Specifically, when taking the Armorer subclass for an Artificer can you use the cantrips Booming Blade and Green Flame Blade with the Thunder Gauntlets provided by the Guardian Armor Model?
This is intended to talk about whether or not properties of the "base armor" used for the Arcane Armor be transferred over to the extended parts of it (gauntlets, boots, helmet). There is a thread that talks about the magical properties of the "base armor" and whether or not that is transferred to other parts as well.
So the way I see it there are 2 interpretations:
-
Properties of the base armor transfer over – Therefore your Thunder Gauntlets will have an associated cost related to your base armor and be able to use the cantrips Booming Blade and Green Flame Blade. However when using magical armor for your Arcane Armor you will not be able to infuse the "extremities" because the magical property was also transferred over.
-
Properties of the base armor are not transferred over – From a game mechanics perspective Thunder Gauntlets are considered separate items from the Arcane Armor and since no such item exists in the PHB the cost is undefined therefore unsuitable for the cantrips Booming Blade and Green Flame Blade. This does mean that while using magical armor as the Arcane armor the magical properties are not transferred over and the extremities are considered mundane objects with respect to infusions.
All in all, which interpretation is correct or is there another interpretation?
Best Answer
There should be no problem with using these spells in combination with an Artificer's Thunder Gauntlets.
The gauntlets count as weapons for the Artificer, and it should be obvious that a pair of armored gauntlets is worth some amount of money, whatever that amount is, so it ought to meet the requirement even if we don't know what the actual value is.
The purpose of adding the 1 silver piece cost to the weapon component of booming blade and greenflame blade was to fix a weird exploit related to component pouches, according to a tweet by Jeremy Crawford:
A component pouch "hold[s] all the material components and other special items you need to cast your spells, except for those components that have a specific cost." Since booming blade and greenflame blade had "a melee weapon" listed as a material component, but didn't list a specific cost, in theory this allowed a caster to just produce a melee weapon out of their component pouch in order to cast the spell, which then I suppose just vanishes back into the ether (or worse, just hangs around, existing). There are similar issues with using a spellcasting focus in lieu of a material component.
This is all absurd and obviously not the intent of the spell, but to fix the exploit, the devs added an explicit cost to the weapon material component, which happens to be equal to the cost of the cheapest melee weapon in the PHB.
In theory this does exclude weapons that do not have an explicit value, but since that wasn't the purpose or intent behind the update, it really shouldn't be a limitation on the players. As long as you have an actual object that counts as a weapon, you should be able to use it to cast these spells.