Kessar was born a demon in the Mesopotamian countryside. He has absolutely no humanity within him. He is a thing of beauty in his physical perfection and in his ability to be purely evil. He has unbelievable powers. His goal is to make the entire world suffer and to take as many lives as he can. No one has ever shown him kindness and it's a favor he gladly returns to others. He revels in his inhumanity and he relishes killing. He was Sin's second in command until he betrayed him.
In Devil May Cry we first see him. He told Sin they found Zakar first and have him where they can't get to him. Then sent Sin Zakar's finger. After Sin and Katra rescued Zakar he went a caught him again and in the process killed Kytara, a Skotos, and took the Tablet of Destiny. He put the time lock for the Dimme in Zakar's chest so Sin would either have to let the Dimme go or kill Zakar. His one fear is a woman named Ravanah, a demon who eats the flesh of other demons and infants and pregnant women. In the end he teamed up with Stryker. In Dragonsworn, he pops back up again, offering Falcyn his sister in exchange for his dragonstone. Falcyn tries to eat him to suck the knowledge of her location but Kessar vanishes right before he could finish.