Cold iron

Mined deep underground, and famed for its efficacy against fey creatures, cold iron is forged at a lower temperature than normal iron or steel, in order to preserve its properties.

Cold iron weapons cost twice as much as their standard counterparts.

Trivia

 * On the Sword Coast North, the town of Phandalin is a major source of cold iron.
 * The rare Holy Avenger blades prized by paladins are forged of cold iron.