What Sylvania needs is some kind of Warpstone magnet, strong enough to pull all the Warpstone (dust?) that was pumped into the ground by Vlad right up out of the ground. That sounds like the sort of thing that'd be catastrophic in the wrong hands, but aside from pulling Morrslieb out of the sky* I'm not actually sure that it would be all that dangerous in the hands of an enemy.
And then, of course, you'd need somewhere to dump all of that Warpstone. There's presumably a given quantity of Warpstone that's actually more dangerous to have lying around than opening a rift to the Warp to dump it into. Maybe throw a captured Brass Orb at it?
*Due to the tyranny of the inverse square law, you'd probably need something much more directed to manage this anyway, like a tractor beam.