Being a cockroach hybrid is not fun. It makes people sad. This is what happens to Gregor, who is a cockroach hybrid that is sad. After the Smoke War, Gregor has been desperately trying to find his place in society. He has not been able to, being a cockroach hybrid, so he resorts to smoking and sinning as a Sinner. Plus mommy issues (thanks Hermann!).  

Gregor's voice is medium-low pitch with a friendly tone within. That friendly tone is mixed in with a tired facet—the tired  that you get after years of being lost in life, not the exhaustion kind. He's just someone going with the flow, an easygoing nature mixed with gruff voice to meld into a tired ol' cockroach man. Poor guy.