Questioning whether this works RAW. I think it does because specific beats general and the specific wording of Invoke Duplicity overides the general ruling on weapon attacks, reach and .
Relevant wording:
Invoke Duplicity:
..... For the duration, you can cast spells as though you were in the illusion's space, but you must use your own senses .....
Booming Blade:
Range: Self (5-foot radius)
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. .....
Given the underlined text you are considered to be in the illusion's space when you cast the spell, and if you are in the illusions space you can make the attack as part of casting the spell (as long as the illusion is within 5 feet of the creature).
Thoughts?
Relevant wording:
Invoke Duplicity:
..... For the duration, you can cast spells as though you were in the illusion's space, but you must use your own senses .....
Booming Blade:
Range: Self (5-foot radius)
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. .....
Given the underlined text you are considered to be in the illusion's space when you cast the spell, and if you are in the illusions space you can make the attack as part of casting the spell (as long as the illusion is within 5 feet of the creature).
Thoughts?