Mechanomancers
A Mechanomancer is a Zarth who uses Wielding to create and power mechanical devices. Mechanomancers should be able to exert their own life energy as well as pouring their power into their craft.
Mechanomancers can convert magical energy to mechanical force, or vice-versa. Thus, most Mechanomancers carry tightly wound springs to fuel their spells. Most squads in the Regiments carry at least one Mechanomancer to allow their soldiers to use magic without becoming exhausted or reducing their lifespan.
Mechanomancers also craft mechanical devices such as weapons, mining tools, vehicles, and energines. They are engineers of a sort.
Of course, this can also be reversed, with mechanical energy channeled into extending the life of a Zarth. Thus, rich or skillful Zarth can live a very long time. (discuss?)