I wanted to challenge myself to do more studies on value and tone. It's not enough for me to simply know how to move a character. I have to understand the environment and how a character moves within it. It also helps me to plan better shots. Before starting on a mega-huge-epic matte painting, you have to understand the fundamentals. This started with a simple sketch I did that looked like an underground cave. Why not expand on it? Don't let it sit there in the sketchbook.
Here is the sketch I started with.