Surtur for Thor Ragnarok

Concept art for Surtur in Thor Ragnarok. Body and face. This one is the one appearing in the movie. With some few previous variations. The director Taika Waititi came with the idea of seeing the skeleton through the fire. So it evolved into some kind of plasma allowing to see through and have some sense of radiography. You can still see the inner structure underneath. Solar eruptions were also one of my references for this.