Does an Arcane Archer fighter's Piercing or Seeking Arrow pass through a Wind Wall spell?

Question

The spell Wind Wall is pretty handy for deflecting projectiles:

Arrows, bolts, and other ordinary projectiles launched at targets behind the wall are deflected upward and automatically miss.

But the two of the Arcane Shot options of the Arcane Archer can't miss.

The Piercing Arrow option says:

[...] When you use this option, you don’t make an attack roll for the attack. [...] [...] The arrow passes harmlessly through objects, ignoring cover. [...]

And the Seeking Arrow option says:

[...] When you use this option, you don’t make an attack roll for the attack. [...] [...] The arrow flies toward that creature, moving around corners if necessary and ignoring three-quarters cover and half cover. [...]

Now, neither of these seem to be written with the possibility of Wind Wall in mind.

Ultimately, I want to know if either of these can pass through or circumvent Wind Wall? I can see multiple arguments either way: that arrows with Arcane Shot options applies aren't ordinary, that the wall of wind is not an object, and that it would be treated as giving full cover. Or possibly, depending on field of battle, that the seeking arrow having to travel 80+ feet around the sides runs out of 'range' (Although it's unclear which range the arrow uses), as the ability doesn't mention going up and over cover (if it did, it could ignore full cover, right?).

So which wins? The immovable Wind Wall, or the unstoppable Arcane Shot?

Answer 1

A Seeking/Piercing Arrow is certainly not an "ordinary projectile".

Wall of wind conveniently identifies for us what projectiles it stops:

Arrows, bolts, and other ordinary projectiles launched at targets behind the wall are deflected upward and automatically miss.

Are Seeking and Piercing Arrows "ordinary projectiles"? Well, do ordinary projectiles do this:

The arrow passes harmlessly through objects, ignoring cover.

The arrow flies toward that creature, moving around corners if necessary and ignoring three-quarters cover and half cover.

Certainly not. Given these things, I would rule that Seeking and Piercing Arrows are unimpeded by a wall of wind.

Does this open a can of worms? Maybe.

Ruling this way then begs the question: are all magical projectiles extraordinary with respect to wall of wind? This is a place for the DM to use some discretion in their rulings, and a place for the players and DM to discuss those rulings. An Arrow +1 is not an ordinary projectile in this sense that is hits harder, and magically so, than a mundane arrow. But does it have any extraordinary properties that would help it defeat a wall of wind? Certainly not in the way Seeking and Piercing Arrow do.

Answer 2

Plain text is the key.

Let's look at the text. The description of Piercing Arrow says:

You use transmutation magic to give your arrow an ethereal quality.

The the most relevant property of being ethereal is to be able to pass through things on the Material Plane. A few spell effects extend to the Border Ethereal, and Wind Wall isn't one of them.

The description of Seeking Arrow says:

Using divination magic, you grant your arrow the ability to seek out your target, allowing the arrow to curve and twist its path in search of its prey.

The text of Wind Wall mentions in several places that it blows upwards. Regardless of whether or not the arrow is deflected, if there is still a valid path to the target, it would still curve and seek.

The fifth-level spell Wall of Force has the properties you want, not the third-level spell Wind Wall.