Automatons. Ever since the whole Steampunk boom (and perhaps preceding it, really), Automatons have been pretty popular in RPG circles. From Promethean: the Created, to Warjacks, Modrons, Golems and Warforged, there’s something about having mechanical beings that behave like humans that fascinates and frightens us.
It’s no surprise to find that the Unborn are in Fantasy Craft to represent this much-loved stereotype. The Unborn is really meant to be a sort-of catch-all race for reanimated corpses, clockwork people, or beings of living brass or steel. The single unifying characteristic is that you were built for a purpose, and given life by technology or magic.