On the left you can see a screengrab of the scene setup.
As always, it's the art of illusion - build as much as you
might need to see, but no more. So in many respects it
resembles again a table-top diorama with enough ground
to move the camera across and provide a horizon, the
castle of course, and some random rounded shapes to
a wood on the far right.
Crucial to achieving some of the effect was to add drifting smoke, first generally across the scene, but also as smoke from a fire within the castle courtyard, adding a sense of life and things happening.
Below are two screengrabs illustrating the setups used to do the general drifting smoke (on top), and then the fire in the castle. I could describe the minute detail that goes into a simulation like this, but you may lose the will to live, so suffice to say the tools allow us to create particles that we design to render as smoke, and wind and turbulence to simulate the movement of air that pushes them around.