How does Wind Wall interact with Cloudkill?

Question

From the description of Wind Wall:

The strong wind keeps fog, smoke, and other gases at bay.

From the description of Cloudkill:

It lasts for the duration or until a strong wind disperses the fog...

So, it seems that if the Cloudkill were cast in front of the Wind Wall, it would be kept at bay, according to the description of Wind Wall. Or, would it be dispersed as stated in Cloudkill?

What if the Wind Wall were cast down the center of an existing Cloudkill? Would it be dispersed only in the area of the Wall? Or would the entire cloud be dispersed?

Answer 1

The spell cloudkill creates a "20-foot-radius sphere" and wind wall creates a wall "50 feet long, 15 feet high, and 1 foot thick".

So, each spell does exactly what they say it says it does.

If the Cloudkill were cast in front of the Wind Wall, it would be kept at bay, or, would it be dispersed as stated in Cloudkill?

This is how I would as a DM, with the information above. I would just as happy with a DM ruling the other way because this is an interesting edge case.

The strong wind from wind wall isn't acting like a normal wind, it isn't just blowing everything everywhere in the direction of the wind. So, it wouldn't blow the whole cloud away, but it would separate the cloud where it was cast. The sizes of these things matter. The wind wall would cut the cloud with a 1 foot line from top to bottom (assuming both were cast on the ground).

If the Wind Wall were cast down the center of an existing Cloudkill Would it be dispersed only in the area of the Wall? Or would the entire cloud be dispersed?

I personally would rule that the ony the 1 foot path would be carved out, as stated above, for the reasons stated above.

Answer 2

It would only be dispersed where the strong winds are

The Wind Wall spell only creates strong winds within its AoE: outside of that 'normal' winds apply. Since Cloudkill depends on these 'normal' winds not being 'strong', the Cloudkill effect is ended where it overlaps the Wind Wall.

Answer 3

I would be forgiving and allow the wind wall spell to dissipate the cloudkill.

Here is why:

Delving deep into the minutia of every spell is less efficient than it was in previous editions because in 5e we tend to have fewer spells to work with. I've also noticed that the spells they do list in the PHB are broader in their utility. I assume this is intentional.

Cloudkill is a brutal spell with the capacity to kill players off very easily. In most games where I've run afoul of it, I've also noticed people forgetting that you can't see through the fog. It's just a template slapped onto a grid board, not "Oh damn I'm being poisoned and I have no idea what's going on around me right now."

If one of your players thought to use a precious spell slot to prepare wind wall (which in my mind is a very situational spell) thinking it would save him from magical mustard gas, good for him.