He's a magician. He uses smoke magic. Preaching existentialism, he is one of the rogue mages defying the Church's iron grip on the population. He is known as Renoir and has lung disease. His life is going to end. He's going to act. BAM!
He sorta fights by blowing smoke at his opponent shaped by magic. For example, he can create a smoke shield to block incoming arrows or create a lion of smoke to attack his enemies. He's pure baddass and likes to quote Sartre.
No one knows the full extent of his smoke magic. Some say he can even turn his body in smoke and dissapear but that's just crazy ain't it?