Ghostrock

This pale green stone, apparently unique to Numeria, plays an unknown role in animating the mechanical Brassmen. As the Brassmen originated in outer space, it stands to reason that ghostrock arrived in the same wreckage that they did, forced deep underground by the impact.

According to the Overseer, ghostrock is pulverized in order to release its power, and this energy fuels the Brassmen and their mighty techno-mystical weaponry. The exact process is unknown, and even the Overseer admits this is only a rumor.