a material strong enough -- the slavemaster 's cells might be reinforced with iron , probably not steel -- a concrete cutter made of steel , then , would be strong enough -- use kinetic energy , yes , a spinning blade , but not a solid mass that could shatter -- perhaps many discs , anchored to a central hub -- hard to say how deep it would need to cut -- no more than a forearm 's distance , probably , the slavemaster would n't waste material on ten-tror-thick walls for a minor prisoner -- cutting blades in a circle with a radius of a tror and a half , need a large motor to maintain rotational speed -- the dark crystal 's light could easily power it , but there was n't a network connecting the light , the larantine had n't arrived yet , drat that hunter , slow and unreliable no doubt , no doubt at all , bah ! -- yes , use the bonestone object to store a charge , it would only take a coating of metal over the words and the handle , such a strange design , whatever could it have been made for ? -- no time , skektek , no time , begin fabricating the blades -- some tolls later , most of the scrap steel was gone and a spoked spinning wheel on a sturdy rod axle was surrounded with razor-edged chunks of metal .