The burning skull symbolizes the spirit of the mountains or a dormant volcano. This is the heart of the mountain. Someday it can break free and bring a lot of grief to people, but the great spirits of heaven are controlling this powerful force.
No, I didn't know about it. Thank you for telling me, I think you know alot about the properties of iron and secrets of working with this material. In any case, you've got some ancient knowledge of the Iron gods!