The magnesi are composed entirely of energy. Each magnese has a magnetic field that picks up magnetite and uses it to make calculations. To reproduce, a magnese will grind magnetite off a worldworm and split in two. The magnesi are known to be sentient, and they are a warlike people, feeding their enemies to the Worldworms. Since the magnesi are much faster than the Worldworms, this is the only way a worldworm can catch a magnese.