Does Lightning Arrow work with an Arcane Archer's 'Piercing Arrow'?

Question

The Arcane Archer arcane shot abilities 'Piercing Arrow' (and incidentally 'Seeking Arrow', which causes far fewer issues) say:

When you use this option, you don’t make an attack roll for the attack. Instead, [...]

However, if I had previous cast Lightning Arrow, which says:

The next time you make a ranged weapon attack during the spell’s duration, the weapon’s ammunition, or the weapon itself if it’s a thrown weapon, transforms into a bolt of lightning. Make the attack roll as normal. The target takes 4d8 lightning damage on a hit, or half as much damage on a miss, instead of the weapon’s normal damage.

Following the rules for Arcane Shot, as I

fire an arrow from a shortbow or longbow as part of the Attack action,

And I...

apply one of your Arcane Shot options to that arrow.

I choose to apply the Piercing Arrow option. At this point I haven't rolled resolved the attack, which is a good thing as by then it would be too late. But I've still taken the Attack action to make a ranged weapon attack.

I know that:

if you're making an attack roll, you're making an attack.

But I don't think that necessarily implies the opposite, i.e. if you aren't making an attack roll, you aren't making an attack.

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As an aside, the only other time I know about one kind of attack becoming another is Grappling and Shoving:

When you want to grab a creature or wrestle with it, you can use the Attack action to make a special melee attack, a grapple. [...] you try to seize the target by making a grapple check instead of an attack roll [...]

Using the Attack action, you can make a special melee attack to shove a creature, [...] [...] Instead of making an attack roll, you make a Strength check [...]

Emphasis mine.

So these are instances of the Attack action being used to make 'special melee attacks', that explicitly don't make an attack roll. Might surmise that my Lightning Piercing Arrow is still some kind ranged weapon attack (special or otherwise)? Or is it implied to not still be a 'ranged weapon attack' by a rule I have missed?

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So how do I determine what happens? Is the Attack action I took still a ranged weapon attack if I'm not making an attack roll because of the arcane shot? Is that shot option not possible given my arrow is now a bolt of lightning, for ... reasons? If the two do combine, how is the damage from Lightning Arrow applied, and what counts as its 'target'? Or is that attack wasted and the spell fizzles as you can't make the attack roll as normal? If it doesn't fizzle from not having a target, which creatures are considered in range of the splash damage?

Answer 1

The text is unclear, by RAW.

The specific ability (Piercing Arrow) calls what it is doing an attack. The way you use the ability heavily implies it is an attack (Arcane Shot does not specify that you are doing something instead of an attack, as the grappling rules do). However, the general rules state that no attack roll = no attack. Therefore, it is up to the DM to resolve this situation that is not properly defined by the rules, as the rules are at best vague and at worst in disagreement.

If the DM rules that Piercing Arrow is not an attack, Lightning Arrow does not trigger - it triggers on your next non-piercing-arrow-ranged-weapon-attack. Resolve piercing arrow as normal, and Lightning Arrow as normal on the next attack made within its duration.

If the DM rules that Piercing Arrow is an attack (as it states in its specific description, which usually trumps general rules), then you would still not roll an attack roll, as while Lightning Arrow states you roll an attack roll it says 'as normal', aka that you do not change the default state of what you are doing. So if you normally do not roll, then it's hard to say that line applies. Each creature in Piercing Arrow's line would take 4d8+1d6 damage on a failed dexterity save. Then each creature that failed the save vs Piercing Arrow would require each creature within 10' of it to make a Dexterity save vs 2d8 damage, as per the secondary effect of Lighting Arrow, thanks to this line in Piercing Arrow ('On a failed save, a creature takes damage as if it were hit by the arrow,').

Overall, this is significantly more powerful than the expected usage of either piercing arrow or lightning arrow, however. It requires a Ranger 9/Fighter 3 character to pull off. A 12th level wizard has tricks that make this seem not only laughable, but cute. In a game with optimized casters, this is not going to be a big deal. Likewise, taking out several weaker creatures is usually not the major difficulty of D&D 5e at level 12. Ergo, while many may believe the DM should always go with the first ruling, I consider that which ruling the DM should go with depends on the optimization level of their table, and also the tone of their game.

Answer 2

Piercing Arrow is not a ranged weapon attack

The word "attack", more specifically, "ranged weapon attack", has a specific definition in 5e. Piercing Arrow (and Seeking Arrow) deal their damage without making a weapon attack. Yes, you are using one of the attacks provided by your Attack action, but it's not a ranged weapon attack, same as if you used one of those attacks to shove or grapple.

To answer your later questions...

Is the Attack action I took still a ranged weapon attack if I'm not making an attack roll because of the arcane shot?

No, because you're not making a ranged weapon attack, or in fact any attack roll at all. The option does not require an attack roll, so you do not.

Is that shot option not possible given my arrow is now a bolt of lightning, for ... reasons?

No, you just make a shot with your Arcane Shot, which pierces through all targets, dealing Piercing Shot damage, before it disappears. Because you never made an attack roll with the lightning arrow, the effects of Lightning Arrow do not trigger - the arrow never transforms into a bolt of lightning, since that happens when it is used to make a ranged weapon attack, which did not happen. The spell remains in effect, waiting for the first time you make a ranged weapon attack.

If the two do combine, (...)

They do not.

Or is that attack wasted and the spell fizzles as you can't make the attack roll as normal?

The Piercing Arrow works exactly as described. The spell remains in effect, waiting for you to fulfill its conditions by making a ranged weapon attack.

Answer 3

Yes piercing arrow is a ranged weapon attack, and yes it should therefore hit every target (max6) in a 30 ft line.

It’s going to catch you in the splash damage if the first creature is within 5 ft, and it’s possible to hit upwards of 30 enemies with all the splash damage.

There is a ruling about piercing shot not triggering the 3rd part of the sharpshooter feat because that modifies a weapon attack roll which piercing shot lacks, but lightning arrow does not modify the attack roll and so it absolutely should work here:

Ruling by Jeremy Crawford

Question: @JeremyECrawford can Sharpshooters -5 to the attack roll for xtra damage be applied to Piercing Arrow? Thnx

Answer: The third benefit of the Sharpshooter feat requires two things to function: an attack roll and a hit. If a special attack, like Piercing Arrow, includes neither of those things, the feat's third benefit doesn't apply to that attack.#DnD

Further on in that thread another user clarified:

Yes, the piercing arrow (and others) from the arcane archer do not require an attack roll, they do force a saving throw.

That's why cheating out the +10 damage without taking a penalty to an attack roll is not intended to work.

No offense to Mr Crawford but this last interpretation seems more correct to me. Piercing shot since it removes the attack roll should work, but because this avoids the penalty it shouldn’t. Lightning arrow on the other hand has no such penalty. The way piercing shot is written it should cause what was a single attack roll to be replaced by dexterity checks for creatures in the 30 ft line.

If it were my table I would probably rule that the sharpshooter penalty moves over to the dexterity saves for piercing arrow instead.

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Furthermore there is debate on lightning arrow not triggering because piercing arrow is somehow not a weapon attack even though it says in it’s own description that it’s an attack. Have a look at what Crawford said when asked a similar question about the wording of piercing shot:

Question @JeremyECrawford @SageAdviceDnD XtE is an amazing book and has created just as many amazing questions. Here's mine: is piercing arrow considered an 'attack'?

Answer The text of Piercing Arrow refers to the attack that delivers it. That means it's part of an attack, even though it doesn't involve an attack roll. It's exceptional that way. #DnD

So if you want to rule against combining the lightning and piercing arrows you have to do it purely on the basis that lightning arrow mentions “ Make the attack roll as normal” and piercing arrow says: “When you use this option, you don’t make an attack roll for the attack.”

Although this is the perhaps same basis on which Crawford invalidated piercing shot and sharpshooter being combined, it seems to me like our piercing lightning combination is operating as intended even given the mention of requiring taking the attack roll both because Lightning Arrow uses the words “as normal” to describe that roll and because there’s no penalty as with sharpshooter. Besides it’s awful flavor wise to think that an arcane archer/caster can’t actually use these arcane arrows with actual arcane spells, so I’d give it rule of cool for sure personally, others may prefer an extremely conservative interpretation of the sage advice on piercing arrow however in which choosing piercing arrow removes the trigger of a normal ranged attack roll for lightning arrow personally that seems highly illogical to me.

Answer 4

Yes

When you use this option, you don’t make an attack roll for the attack. Instead...

This specifically calls is out as still being an attack, but a specific type of attack (with a different method of hitting), and since specific beats general all the other more general means of deciding what is an attack are superseded.