"The brass orb, which we've found mention of in the Skaven writings under the imaginative name of 'Brass Orb', is basically a Pit of Shades except, uh, worse in every conceivable way. It cracks open a rift all the way to the Aethyr which sucks in everything and everyone in the vicinity, which is only most of the time clogged with viscera and debris before anything nasty can make its way through from the other side. The intended use is as something like a grenade, except the activation sequence makes its weight and inertia impossible to predict from moment to moment, so half the time it ends up overshooting or undershooting the mark. There was some discussion of using it to get rid of some things we really don't want to remain in reality any more, but most of them would be even worse in the hands of some of the denizens of the other side, so in the end we just had the navy drop it on an rocky outcrop off Norsca and blew it up with a barrel of gunpowder. Just seemed like it would be tempting fate to do anything else with it.