A step by step process. There were 24 sketches before we settled on our eventual image. Here is a sampling. They initially wanted us to be inside the mausoleum with our villain.
We took it outside, changed the look of the mausoleum, and reduced the real estate of the snake scene. It was during this phase of development that we had to eliminate the moon as it was determined we are looking north. Fortunately we were able to pull light from the fog over the River Thames beyond the horizon line.