So there are 3 kinds of golems so far. They are all animate, but only two of them have Motion. Two are Erf magic, but one is Fate magic. I'm going to ignore Hat Magic golems for the moment (the reason for which will become clear at the end).
We have several pictures of dolls and dirts. The thing that strikes me most immediately is that all dolls we have seen have either been made from flexible materials, or have had joints. The dirtamancy golems don't. Even in the new erfabet art, we can see the dirts don't have working articulation, but the dolls do. On top of this, one of the disciplines next to Dollamancy on the chart, Croakamancy, seems to work by using magical locomotion to enhance muscles as seen here:
My theory is thus; that the so called G-Strings function in both Dollamancy golem bodies, and certain uncroaked like the skeletons, as a synthetic muscle system. When the strings contract, they pull on the "skeleton" of the unit providing mechanical means of motion. This is why the Dolls must have joints if they aren't made of flexible materials.But the craft of the Croakamancer was to understand the body's condition, its functions, its strengths and weaknesses. The Croakamancer could conserve the fuel of the body by focusing her juice upon the mechanisms of its movement, repairing and augmenting them with magic.
On the other hand we have the jointless Dirtamancy golems. Dirtamancy is Erf magic, which in Book 0 is partially explained here:
I propose that whatever mechanical force is moving the Dirt golems, the enchantment isn't the G-String based muscles of a Doll, but instead has something to do with the "firmament" and in fact has no direct analog to a musculature system. Further support of this theory is the fact that unlike any dolls scene so far, the crap golems appear to be completely amorphous, held in their shape by magic rather than any rigidity.In addition, this rock golem appears to be healed in such a way that it's body is mearly being held in shape, but the arms still move without joints. I further propose that this same "kind" or class of enchantment is also behind the hat golems, rather than Hat Magic having a unique form of animation for it's golems.Which is all to say, I have no idea how the dirts are moving, but am betting it's a mechanism that doesn't require actual working joints. The biggest problem with this theory is we have never seen a dirt golem (other than the tin golem) in Xin's art style.This thread was being drawn up by the system of the world. Thinkamancers knew it as a "Grandiocosmic string." Its numbers were being shaped and guided by the firmament, by what magic theorists called the Erf Axis.
The only unit not taken into account with this theory is the tchotchke. And currently we don't really know what they are.
So, this is my crazy theory about how the golems work in-universe. You like it? If not, what's yours?
Added more Dirtamancy golem thoughts.