Silver weapons are crafted with a hardened silver/steel alloy. These weapons are among the few that will cause damage to spirits and are one of the only non-enchanted weapons (the other being Daedric weapons and high level Hand-to-Hand) able to do so. Silver weapons begin appearing randomly in the world and on opponents after level 4. The Imperial Guards, along with all other city guards, are equipped with Silver weapons, so as to combat any ghost-like creature or vampire that they may come across (or any that you summon).