So here is my critique.
The good: as was stated solid shading good depths here giving that three dimensional look. Next you have a good expression here very much so conveys a seriousness. Your concept of a new mask is a good one as well.
Needs work: your left eye is off in shape it is a bit to rounded at the left most end killing your facial symmetry. Your chin is a bit long I would use your own chin to get the dimension here. The left most lightning bolt due to shape and shaping gives the impression of sticking straight out vice being swept back. Lastly the neck seems a bit on the thick side. I would consider sliming it down.
Overall: you have a great eye for detail and a clean quality to your work. You are good at emoting an expression which can be so difficult. I also suffer from symmetry and proportion issues so from one facial artist to another all we can do is practice practice practice.