Do flying creatures count as anchor points for the Web spell?

Question

Several size Large flying creatures are attacking my party. I'd like to cast Web to prevent their escape and limit their ranged advantage.

Relevant parts of the Web spell description say:

The webs fill a 20-foot cube from that point for the duration. [...]

If the webs aren't anchored between two solid masses [...] the conjured web collapses on itself

I can get at least two of these creatures to be affected by the spell's area of effect. Would they count as the 'two solid masses' the description requires?

Answer 1

Technically, no

Going by the plain English reading of the word "anchored", the web must be attached to a fixed position.

anchor verb past tense: anchored; past participle: anchored

1.

• secure firmly in position.

• provide with a firm basis or foundation.

The two examples supplied in the spell description are walls and trees, so it seems evident that the 'position' or 'firm basis' required is a solid mass fixed relative to the ground. And, arguably, attaching something to a moving flying creature is not "secured firmly in position" relative to the ground.

Plus there is the fact that if you did count creatures as anchor points then there would be no reason that you couldn't use non-flying creatures as well and then there would be no point to the caveat in the spell description in the first place!

Answer 2

You could certainly use a creature as an anchor point, provided the creature is of a sufficient size.

Nothing in the spell description says that you can't, and 5e went with the design philosophy of "it works how it says it works". It states that you need "two solid anchor points" with only a loose guideline on what that constitutes. As long as they're not Dread Wraiths or something else incorporeal, they should be targetable.

That being said, the web doesn't stop them from being able to fly, and if you end up being able to only catch two of them in the webs area, if either one of them successfully makes their save or moves more that 20' away from the other, the web looses one of its two minimum anchor points and collapses in on itself, freeing the other one as well. Realistically, you'll probably only stall them for a round or two.