can a Wall of Force or Stone spell be used offensively?

[Degwerks]

Going to be fighting an adult dragon soon, and I'm wondering if I can use a wall like force or stone to ready an action to cast it in front of a charging flying dragon. How much bludgeoning damage could that do?

[RickAllison]

I would say he has enough control at that speed to not take damage. It can be used offensively in other ways, however. Cutting off retreats, trapping the dragon near the ground, keeping minions and such (or the dragon itself) stuck while the party deals with other enemies. Oh, and the party can ready actions for a one-shot attack.

[MaxWilson]

You can use Wall of Stone to trap the dragon in a space too small for it (giving it disadvantage on attacks, and you advantage to hit it, per Squeezing Into Smaller Spaces rule in the PHB) while leaving an opening large enough for you to shoot through it. It will be able to tear the wall down eventually but oh well.

If you can get the dragon to use its reaction before the spell goes off--e.g. on an opportunity attack or a Counterspell--the dragon won't even get a saving throw against the spell, since the Dex save for Wall of Stone merely enables the use of your reaction to move*.

The big problem: it doesn't work if the dragon is in midair, because the wall must rest on an existing stone foundation. (I suppose the stone stone must be extruding from the existing stone?)

* And by the way, it is extremely odd that humans a "free" burst of speed (adrenaline?) only when a wall of stone is about to appear, but not when they're about to be eaten by a dragon or an owl bear.

[krugaan]

Bob the Wizard: "I cast wall of stone! Thicker than a barbarians skull, but maybe not quite so hard!"

later that night...

"In other news, the Barbarian Anti-Defamation Coalition put out a statement today condemning Bob's classist remark as 'deeply offensive' and that they would 'be all over [him] like white on rice on a paper plate with a glass of milk in a snowstorm.' Bob was unavailable for comment, and all attempts to scry his location were defeated by non-detection.

And now, Anne for the weather."