[Here, Mr. Demon, try an actual human suit on for size.
The history is nothing Sebastian doesn't already intimately know, but oh the feelings of it all. The devastation at discovering his parents' burning bodies, the humiliation and despair as he's sold, branded and tortured, and treated no better than a beast. A month of this, piled on and compounded until it culminates into the vindictive satisfaction he'd felt at all of the deaths Sebastian caused, mere moments after they'd formed their contract.
And how beautifully efficient Sebastian had killed for him. What driven determination he'd felt.]