Swamped

You're not prepared to commit to Corvus' explanation. You don't see what else these people might do with a large quantity of water, other than drink it if they're very thirsty, but right now the data isn't pointing to the flooding theory.

"Dominique. You're the ether expert, what options have we got for disrupting a spell from this distance?"

"Anyone with ether manipulation can do it, in theory. You just reach out to the ether and pull it towards you. There's two problems. The main one is, the wizard can see where it's going, so doing it stealthily isn't an option. The other is, I'm the only ether manipulator we've got here and I can't do much of it on my own. I could still disrupt the spell, but it'd take several minutes for me to pull an appreciable amount away. I have equipment that can do it more efficiently, but all of it would require getting close to the wizard."

"That's messing with the spell directly," you muse. "Any other way to do it?"

"Well, hypothetically if you produced a large quantity of ether all of a sudden, it would make the spell behave unpredictably. If that happens the safe thing to do is cancel the spell and try to deal with the ether. Problem is, there are very few ways to do that and they're basically all out of our control. Unless one of you has secretly been a god this whole time."

"That would have made a lot of things much easier," you sigh. "So that's it?"

"Unless you've got a few pounds of silver, or some other even rarer ether-resistant metal, pretty much."

"Silver actually works? I thought that was just a story."

"Not that well, but it does have an effect. And for something like a gateway, you'd want precision. You'd still need a good chunk of silver, but it would probably be enough to throw the spell off."

"Too bad we don't," you sigh. "Sounds like the easiest option."

"Done!" Gregor suddenly shouts. You stare at him.

"Done what?"

"Oh, sorry. When Ms. Dominique mentioned silver, I had an idea."

He points down to his cauldron, which is filled with a silver liquid.

"Is that quicksilver?"

"No! It is silver, liquified and mixed with something a bit more... volatile. Drop it down, and the hole will fill with silvery smoke. Enough to disrupt the spell, perhaps?"

You glance at Dominique.

"It might work? Each bit of silver would only have a little effect, but if it's all spread out, that could really cause serious interference. But it's not something I've ever tested. On the other hand, I can't say I have any other ideas."

"It's still going to get a wizard mad at us," Corvus points out.

"Well, if it works, then it should disrupt any spells they might attack us with. Of course, I wouldn't assume a wizard doesn't have tricks other than magic."

Well. Do you go along with this plan or not?