Considering the span of time the game takes place in, would it not be inconceivable for the game to eventually reach some sort of diesely-early 20th century with giant robots powered by demonic energies, built with the intent of reducing labour needs rampaging through the lands?
Would giant robots with the capability of destroying buildings be something moddable?
Things on tracks (in other words, train-like things) would be easy enough for that sort of tech... Free-roaming robots, particularly on natural terrain, requires much more work. By their very nature, such things would be VERY* heavy, and thus prone to sinking into the ground or getting stuck in a pit if conditions are anything less than ideal. I would say you would probably be better off keeping such things at least on solid ground able to support their bulk. Rails or tracks of some sort would have the strongest historical precedent; before self-propelled trains, they saw use similar to Dwarf Fortress minecart tracks for wagons and other large loads, and their use goes back thousands of years. And if the vehicle's necessary weight requires sturdy ground to be constructed and leveled, tracks are probably easier anyway and removes the need for ever-finicky steering devices. So giant robots would largely only make sense if confined to some form of rails or tracks.
*Bronze, brass and copper have densities around 8-9g/cm^3; which means a single cubic meter of the stuff is 8500 kg. The biggest advantage modern robots have over steampunk robots, aside from the ability for them to have easily created control software, is weight. More modern materials and alloys, like plastics and aluminums, are more like 1-2g/cm^3. Taking into account additional structural needs due to this added weight in combination with more bulky fuel, power, and control systems: you're looking at really heavy robots. Anything short of durable rails or a meter of poured concrete, and I suspect you would find you're halfway underground.