Silver

Silver was a metal which, in human mythology, could be used to kill a werewolf, particularly in the form of bullets. The First Doctor used silver bullets to kill Roberta Sampson, a werewolf. (PROSE: The Juror's Story) Silver bullets were also utilised by the Brigadier to defeat the Destroyer. (TV: Battlefield) Similarly, Rosa Caiman had a silver knife to defend herself against werewolves. (AUDIO: Loups-Garoux)

A Dalek taskforce sent to Exxilon has silver casings. (TV: Death to the Daleks)

The planet Megerra was rich in valuable minerals such as silver. (PROSE: Shakedown)

Silver Daleks with blue were present on the temporary base the city of Andor on Moldox. (PROSE: Engines of War)

When forced to create EDTA to cure arsenic poisoning, Gwen Cooper used a number of ingredients in the antidote, one being silver. (TV: Rendition)

Silver had an atomic weight of 108 and high conductivity. (PROSE: Castrovalva)