Primium

Primium is a metal made from alchemically purified silver and gold. It retains the mystical properties of both of those metals to harm changing breeds harmed by such metals, and it is contains anti-magical properties to cancel supernatural or magical attacks and defenses.

Very few Mage groups have the knowledge to be capable of creating the expensive metal:
 * Iteration X
 * Sons of Ether
 * Knights of the Temple of Solomon (Knights Templar)
 * some within the Celestial Chorus (namely those that defected from the Knights Templar)