So, used Paint Tool SAI 2 to do this interior scene work.

Why in the fuck have I not used SAI earlier??

Following on from the landscape I did earlier, the idea is that the resin reacts with sunlight to become soft, spongiform and somewhat elastic, the deeper inside the burrows, the less elastic, darker, and more like obsidian. The reason is twofold; structural flexibility, and the smooth, organic shapes help to focus sound and airflow into the burrows - sort of like an ear, or, well, what it looks like. :P