Caltrop
this was a generic term used to describe a form of defensive implement formed from a central sphere of metal, to which were affixed a minimum of four metal spikes. The minimum of four spikes ensured that, when thrown, the caltrop always presented an upright spike. When a large number of caltrops was thrown or deployed across a room's floor or entranceway, they provided a screen which a pursuer had to avoid, or else have the metal spikes driven into their feet. Especially devious individuals coated the spikes of their caltrops with sedatives or poisons, in an effort to ensure their escape.