From House of Hozz
Mechanomancers should be able to exert their own life energy to do magic, as well as pouring their power into their craft. Zarth magic relies on sacrifice, whether self sacrifice, or the sacrifice of others. This makes the "magic" of the Zarth much more mechanical, and focused, than that of the fay.
Tribal magic, a whole tribe sacrificing to power one Zarth's magic?
Drawing on sacrifice along the lines of the Regiments?