[RPG] Can you combo attacks with the Booming Blade cantrip

attackcantripsdnd-5espellstwo-weapon-fighting

I understand that so long as conditions are met, you can Sneak Attack as part of the melee attack from the Booming Blade cantrip.

Can you dual wield and attack with both weapons after casting Booming Blade? I understand that you probably need something like the War Caster feat and Subtle Spell to pull this off, but I don't know if the melee attack as part of Booming Blade is a bonus action or not.

Can you extend the combo if you had Extra Attack like those from either fighter, ranger, monk, or bard, and use damage-increasing spells like Hex or Hunter's Mark? It's safe to say this build is around Lv 5 or higher.

So is the following combo possible?

  • Build (Human Rogue 4, Ranger 3, Sorcerer 3)
  • 1st Round: Full round act: cast Hunter's Mark and Hex.
  • 2nd Round: cast Booming Blade swing with main hand weapon [weapon + d8 + 2d6 sneak attack]
    then swing again (if with extra attack) [weapon + hunters mark 1d6 + colossus slayer 1d8],
    then swing with off hand [weapon + hunters mark 1d6 + colossus slayer 1d8]

Now if you dip in fighter, can you add Action Surge so you can get two more attacks from your main hand for a possible [2x weapon + hunter's mark 2d6 + colossus slayer 2d8] damage? And 2d8 thunder damage if the targeted enemy goes after the attacker (me)?

Best Answer

No, You cannot combine attacks with booming blade.

Both Booming Blade and Green Flame Blade say the following:

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

This means that these cantrips do not require you to take the Attack action, they require you to take the Cast a Spell action.

If we look at extra attack, it is defined as:

Beginning at 5th level, you can Attack twice, instead of once, whenever you take the Attack action on Your Turn.

No Attack action is taken, so no extra attacks can be used. Additionally, two weapon fighting states:

When you take the Attack action and attack with a light melee weapon that you’re holding in one hand, you can use a bonus action to attack with a different light melee weapon that you’re holding in the other hand.

Again, no attack action is taken, so you cant use a bonus action to make an off hand attack.

In your scenario, you can cast hunter's mark or hex, and then the hit from the booming blade will trigger those effects, as well as sneak attack (if the conditions are met), but you will be unable to make more attacks after that.

Action surge gives you another whole action, which you can use to cast a spell, like Booming Blade which will give you one more attack, or if you just use a regular attack action, extra attack and two weapon fighting could apply.