When the player kills a giant spider with an elven dagger and Sting has not yet been created, the dagger is converted into Sting automatically. Sting is made of rustproof steel, instead of wood (this would be tricky to do because of base items; you would still want to be able to create it by naming an elven dagger, but Sting in the lore is made of steel or at least metal, not wood). Sting has bonuses versus spiders, in addition to its bonuses against orcs.