Bartel has slicked-back brown hair and brown eyes. He wears a gray undershirt beneath a simple black jacket with a popped collar and small belt buckles as fasteners.
In stark contrast to Helene, Bartel is absolutely merciless and sadistic. He shows very little concern for human life, and relishes in every opportunity where he gets to kill or torture someone. This is apparent even when the torture is too much or the murder is unnecessary, as seen when he allows a soldier to beat Kenna's master beyond necessity, or complies with the immolation of Duncan, Marco's former weapons master, just to test Hex's cannon. Because they share the same traits, Marco and Bartel always agree with each other.
However, at the same time Bartel is also a coward when he's in the receiving end of a punishment, at least when it's unnatural. When Dom lights him on fire after killing the former's hawk, he frantically begs for mercy (albeit ignorant of the cause of the fire) while running around in a frenzy. When Dom confronts him with a guard's axe, the mere sight of the weapon blazing furiously with Dom's magic immobilized him with fear, whereupon he again begged for mercy.
Bartel and Marco share a friendly relationship, probably because they both enjoy other people's suffering. As opposed to Helene, Bartel agrees with everything Marco decides. Being his right-hand man, Bartel supports Marco's decisions even if they were against Luther's wishes.
Bartel and Helene, despite the fact that they are both loyal to the Nevrakis family, are often at odds due to their opposing ideals.
Dominic has an intense dislike for Bartel for his involvement in Marco's plots against Kenna, which eventually turns into outright hatred after Bartel crushes his hawk under his feet. Dom later kills him either with a flaming axe or a burning grasp, turning his body into ash.