Context

For a relatively new campaign I've built a kensei (monk). At level 7, 8 and 9 (we're level 4 now) I'm planning on taking three levels in swashbuckler (rogue). Now I'm exploring my options for triggering Sneak Attack with this character, in melee.

My character's Kensei Weapons are a longsword and longbow. So with this multiclass idea I won't be able to trigger Sneak Attack with the trusty longsword, or with my Unarmed Strikes, because Sneak Attack states:

Once per turn, you can deal an extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll. The attack must use a finesse or a ranged weapon.

You don’t need advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn’t incapacitated, and you don’t have disadvantage on the attack roll.

Combat situation

When engaged in melee combat, my game plan is to wield a longsword in my main hand and a finesse weapon (dagger) in my off-hand, while still having the rest of my body ready for making Unarmed Strikes (knees, elbows, kicks, headbutts, etc). When the circumstances are right for making a Sneak Attack, I would like to strike with the dagger, without the need for swapping weapons and without taking a bonus action.

Question

My goal is to use my usual attack and damage roll for the dagger when I declare the off-hand weapon attack during my Attack action or Reaction. I would be wielding my longsword too, but not necessarily attack with it on the same turn. Would this work by RAW? Or would I be needing to have the dagger in my main hand for this?

I'm new to the workings of Two Weapon Fighting, so I might be overlooking something here.

Related:

• Rogue using Dual Wield and Sneak Attack

Yes. The character can use the dagger to make an attack.

• When holding two weapons, a character can choose to attack with either.


• If the character opts to attack with both, the rules for Two-Weapon Fighting come into play.


• If the attack qualifies for Sneak Attack, then those rules apply.

In the specific combat situation, the monk can choose to use their attack action to make a melee attack with the dagger.

There is no main hand nor off-hand anymore.

These are concepts that are from previous editions of D&D. The Two-Weapon Fighting rule only concerns itself that two weapons are being wielded simultaneously, and are both light:

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 atlack with a different light melee weapon that you're holding in the other hand.

You can hold a Longsword and a dagger and choose which one you want to use*

*However, you can not attack with both your longsword and dagger in the same turn.

The rules around Two-Weapon Fighting require both weapons to have the light property:

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. You don't add your ability modifier to the damage of the bonus attack, unless that modifier is negative.

So in this build where your monk/rogue is wielding a longsword in one hand and a dagger in the other, they have the option of making a combo of longsword/unarmed in one turn or dagger/unarmed. They can not opt to use longsword/dagger.

You also miss out on that sweet d10

Because you are wielding a weapon in both hands, you aren't wielding that longsword for the versatile d10 damage. That's kind of a primary point for the Kensei (at least until the martial arts die gets equal to it.)

You could just drop the dagger if you feel that you don't need it and go full versatile with the longsword, but then you might not have it when you need it. Unless you pick it up at the start of the next round. The action economy allows it, but it's a bit squirrely and a DM may take issue with it (or you may lose the dagger due to other circumstances either creature or environment related.

Sneak Attack with the dagger is permitted

As you've noted, the dagger does provide everything you need for sneak attack. When the opportunity arises for that damage, then you can choose to attack with it.

There is no off-hand

Since there is no penalty for 'off-hand', other than not adding your modifier to the bonus action attack for TWF (see above quote), this is a completely viable build option.

In 5e, the idea of off-hand is a bit weird. They have transferred the idea of the 'off-hand' to the bonus action attack. Functionally, you are equally proficient with either hand when using your Attack action. It's when you use the bonus action for attacking with a second weapon that you lose your proficiency.

You will still need to make an unarmed strike while holding your kensei weapon to get the Agile Parry

Just a note (in case you were thinking of taking the Dual Wielder Feat to allow the use of non-light weapons) that you still need to make an unarmed strike in order to activate the AC boost.