Really digging this design! It has a very heavy feel, and the reactive armor and the detailing make it very unique. Only thing I'd crit is that the upper arms are too noisy and blend in with the body too much.
The square is like his signature on the piece. You typically see similar things on Japanese traditional art (typically done with a stamp), but he took the idea and made it modern and graphic for his style and target audience.
Anyway, I can totally see the inspiration of the Mantis form. Really cool work!