It's this...glowy blue liquid. Well, usually blue. Hopefully blue.

[Varric mimes with his free hand but what he's miming is anyone's guess.]

It is a little complicated to explain but basically it's magic, in a bottle. But it's also anti-magic. Some humans drink it by the bucketfull so they can stomp out mages, but that is this whole thing.

I don't suggest it. Drinking it makes humans crazy...er. Crazier.