The two metals of primary significance are zinc and brass, which allow you to control expression strength. Zinc wires touching the gemstone will cause the spren inside to more strongly manifest, while brass will cause the spren to withdraw and its power to dim. Remember that a gemstone must be properly infused following the spren’s capture. Drilled holes in the gemstone are ideal for proper use of the cage wires, so long as you don’t crack the structure and risk releasing the spren. —Lecture on fabrial mechanics presented by Navani Kholin to the coalition of monarchs, Urithiru, Jesevan, 1175
