Does the double-bladed scimitar's special attack let you use your ability modifier for the damage of the attack?

Question

I am using the double-bladed scimitar with the Revenant Blade feat from Wayfinder's Guide to Eberron.

The double-bladed scimitar's special feature (p. 74):

Special. When you take the attack action and make a two-handed attack with a double-bladed scimitar, you can use a bonus action to make a melee attack with the blade at the opposite end of the weapon. This attack uses the same ability modifier as the primary attack. The weapon’s damage die for this attack is a d4, and it deals slashing damage.

The part of the Revenant Blade feat (also on p. 74) that mentions the damage:

On your turn, when you use a bonus action to make a melee attack with the blade at the opposite end of the weapon, the weapon’s damage die for this attack increases to 2d4, instead of 1d4.

Let's say I have 16 Dex, so a +3 to my dex mod. If I take the Attack action with the weapon, and use my bonus action for the weapon's special function, do I add my Dex modifier to the damage of the special attack or not? Will it be 2d4+3, or just 2d4?

Answer 1

You can add your ability modifier to damage from the bonus action attack

The general rule for damage rolls is:

When attacking with a weapon, you add your ability modifier--the same modifier used for the attack roll--to the damage.

So, you can add your ability modifier here because nothing tells you that you cannot.

Unofficial guidance from Jeremy Crawford (5e's lead rules designer), which some may consider authoritative, agrees with this interpretation (credit to V2Blast for providing this quote):

"When making a weapon attack, you add your ability modifier to the damage, unless a feature tells you not to.

So far, so good.

But, does this rule for two-weapon fighting, which also grants a bonus-action attack, confuse matters?

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

Don't worry – this rule can be safely ignored. Wielding a double-bladed scimitar, is not the same as two-weapon fighting, and thus two-weapon fighting rules are completely irrelevant to your situation.

Add your ability modifier to damage rolls as you would with any normal melee weapon attack – your damage roll with this bonus action will thus be 2d4 + 3.

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Note: Since this question was both asked and answered the text of the Wayfinder's Guide to Eberron has been updated with the release of Eberron: Rising from the Last War. Credit to V2Blast for pointing out these changes.

The rules quoted in the question above have changed for both the Double Bladed Scimitar (slightly) and the Revenant Blade feat (substantially).

The underlying question here is unaffected by these changes - you can still add your ability modifier to damage you deal with the (reworded) special bonus action attack that the Double Bladed Scimitar grants. However, the correct damage would now be '1d4 + modifier', as opposed to '2d4 + modifier' as the Revenant Blade feat no longer grants an extra damage die to this attack.

Answer 2

Based on the wording alone, I think you have answered your own question.

This attack uses the same ability modifier as the primary attack. The weapon’s damage die for this attack is a d4, and it deals slashing damage.

and

the weapon’s damage die for this attack increases to 2d4, instead of 1d4.

So because of this, you would get 2d4 + ability mod.

Answer 3

Yes directly in the text of the weapon description: The applicable text of the "Double-bladed Scimitar", only cited for clarification, in part.

Special: If you attack with a double-bladed scimitar as part of the Attack action on your turn, you can use a bonus action immediately after to make a melee attack with it. This attack deals 1d4 slashing damage on a hit, instead of 2d4.

This "bonus attack" is NOT off-hand (or TWF at all) so it may have the modifier added, similar to how PAW allows the same.

Additionally: The applicable text of the "Revenant Blade" feat, only cited for clarification, in part.

• A double-bladed scimitar has the finesse property when you wield it

The feat "Revenant Blade" (RB) allows the user the finesse property, so with it either Strength OR Dexterity modifier may be used (BUT you must use same modifier on both to hit and damage rolls)

• Without its RB feat: Strength only
• With its RB feat: Strength or Dexterity, your choice.

The only other option (for Double-bladed Scimitar) is as a pact weapon. Both conjured pact of the blade warlock and/or bonded pact weapon for a hexblade warlock, which would allow you to use Charisma with the Double-bladed Scimitar (See "pact weapon" descriptions, in both PHB & XGtE, for details I wont link here)

• As "Pact of the Blade" Warlock's materialized pact weapon and/or Hexblade's "Bonded" pact weapon (only for the Warlock in question) Charisma may be used

So oddly, its truly awesome for a class it was most likely not intended for.

(I would say its far easier to obtain, & be proficient it without needing to "bond" with it, via the conjured method, btw)

The only other modifier (but not in the Double-bladed Scimitar's case) used in melee in a similar fashion, that I am aware of, is Wisdom BUT this is due to a spell: "Shillelagh" (this brings up bards casting it, once again allowing Charisma in that situation... yikes)