[RPG] What modifiers are added to the attack and damage rolls of this unique longbow from Waterdeep: Dragon Heist

dnd-5emonsterspublished-adventureswaterdeep-dragon-heistweapons

There is a unique longbow in the Waterdeep: Dragon Heist module (p. 201), whose description includes:

This unique weapon can be used only by a Medium or larger creature that has a Strength of 18 or higher. The bow shoots oversized arrows that deal piercing damage equal to 2d6 + the wielder's Strength modifier…

However when looking at the PHB's section on "Dexterity Attack Rolls and Damage", I realized it states:

You add your Dexterity modifier to your attack roll and your damage roll when attacking with a ranged weapon…

To me this means that unless a feature specifically tells you not to, you would add your Dexterity modifier to a ranged weapon's damage and attack rolls.

An example of such a prevention is Two-Weapon Fighting which states:

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

Notably, the NPC who owns it has a +3 proficiency bonus, a +7 to attacks with the longbow and deals 2d6+4 damage. Unfortunately, their strength and dexterity modifiers are both +4 so I can't tell which is being added.

However, as @thedarkwanderer pointed out in a comment in the Q/A "How can I shoot a bow using strength instead of dexterity?":

NPCs use different rules than PC's

This leaves me uncertain and with the following question:
If a PC wields this unique longbow, what modifiers do they add to its attack and damage rolls?

Best Answer

When the text is unclear, look for examples

Surprisingly this relies more on text interpretation than rule interpretation, which is probably where the confusion lies.

Normally a weapon description would list a die number (1d6, 2d6, 1d4, etc.) in a table for the damage numbers. From there it was on the player to know to add your ability modifier based on the attribute used for the attack roll (PHB 194). Unfortunately the damage for this weapon is described inline with the weapon description.

The bow shoots oversized arrows that deal piercing damage equal to 2d6 + the wielder's Strength modifier

has two possible interpretations:

  1. 2d6 + STR is the weapon's base damage and you should add your Dexterity in addition to this
            (if a weapon description said "...piercing damage equal to 1d10+1" then you would expect to add dexterity, after all)
  2. 2d6 + STR replaces the final damage value of a normal bow attack: 2d6 + DEX.

Both of which are valid. In this case the confusion lies in the flavorful wording mixed with attribute modifiers being unusual for weapon damage descriptions.

Use the NPC as an example of the intended usage

The NPC using this bow is an example straight from the designers about how this bow should work and can help us at this impasse. You cite that they are listed as having attacks from the bow with damage equal to 2d6+4, and they have a Strength and Dexterity modifier of +4. Because it is not a +8, we can infer that the bow is intended to use STR instead of DEX and not STR in addition to DEX in the hands of a player. A more accurate version of the text might read:

Attacks made with this bow deal 2d6 piercing damage and adds the wielder's Strength modifier instead of their Dexterity modifier.


The Attack Roll

The PHB(194) has this to say about the ability modifier for Attack Rolls:

The ability modifier used for a melee weapon attack is Strength, and the ability modifier used for a ranged weapon attack is Dexterity. Weapons that have the finesse or thrown property break this rule.

However there is some debate surrounding page 196 where, while talking about Damage Rolls, the PHB says:

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

Where it could be implied that the ability modifier and the attack modifier must match. Because the former statement regarding the attribute-to-range assignment is explicit, directly under the heading regarding attack rolls, and specifically mentions exceptions to the rule, I don't consider the justification strong enough to imply that the weapon would use Strength as the attack modifier because of the excerpt on page 196. It appears to have been meant only to tell the reader that the damage roll attribute normally depends on the Attack roll attribute.

Neither the NPC description nor the weapon description mention explicitly a different attack attribute modifier, and there is no rule stating explicitly that attack attribute modifiers must correspond to the damage attribute modifier.


We are left with the following: The general rule for ranged weapon attack modifiers using Dexterity applies, with an intentional override changing the damage roll modifier from Dexterity (as would normally be inherited from the Attack Roll) to Strength. The bow makes attack rolls adding Dexterity and damage rolls adding Strength.