Cerebrus in the Volcano Picture

Cerebus, the three headed dog that is said to guard the entrace to the underworld, is inside of a volcano.

I made this as a sketchbook for my advanced art class. We were supposed to recreate a dream OR do something with myths. I chose to create a creature of Greek mythology with Photoshop 7 and my Bamboo (tablet).

Impressed with how much depth can be created using cell shading, I decided to see if I could achieve a level of depth that I hadn't been able to do before using only cell shading. How did I do? What do I need to do differently to make my work better?
6 Levels of Hell
Pop-Up Book 2
Cerebrus in the Volcano
Mashile, Spearholder Of Thermal Gae-Bulg
"Good luck, Theseus"