Of the Lathe the Swarf
Of the Lathe the Swarf is a goblin who appears in The Shepherd's Crown as a representative of the new order in the Discworld. Being a mechanically minded goblin, he lives up to his name in the manner of his escape from the Queen of the Elves. A handful of swarf which was indeed taken from the lathe was used to great effect - swarf being fine steel shavings and filings which would, of course, be 95% iron. Throwing it in an elf's face would be like silver filings to a werewolf. His insight is later used with telling effect in the short war with Elfdom.