Lewis Animation participated in pwnisher's Boss Fight challenge (which reminds me, I need to do a roundup of the many awesome Blender entries!). In this video, he walks us through the creation process. Topic covered are blocking out and sculpting the basic shape, rigging it and then moving to animating the key poses. Only then did he dive into the detailed sculpting and texturing in Substance painter. Add a bit of fire and heat, a terrain and a hero, and you have an awesome boss!
This is not a step-by-step detailed tutorial, but a rather high-speed overview of the used techniques.