Here's some work I did of the Torso Boss, the first boss monster we created from scratch as a part of this project. The idea was for it to be a classic upper body looming over the battlefield and clobbering you type of boss, hence the name. I soon shortened the name to Torsobus, as is my way.
Some of these concepts are paintovers of 3D models by Nestor Villegas. https://www.artstation.com/3denvy My art director for these was Ben Zweifel. https://www.artstation.com/benzweifel