"You mean push the acid towards them? By the time the acid gets there it would be nothing but a drop, if we're lucky. Like everything liquid, it spreads out over an area and stops until it can't spread anymore, is soaked into the ground, or evaporates. I don't know where this Dark Empress lives but it's probably too far away for us to push the acid to her. Even if we did manage t do that she would have to step in it for it to work. Now unless your shield can morph into an indestructible bucket then I don't see how we'll be able to melt her face off."